Mucopolysaccharidosis type VI (MPS6) is an autosomal recessive lysosomal storage disorder resulting from a deficiency of arylsulfatase B. Clinical features and severity are variable, but usually include short stature, hepatosplenomegaly, dysostosis multiplex, stiff joints, corneal clouding, cardiac abnormalities, and facial dysmorphism. Intelligence is usually normal (Azevedo et al., 2004).

Purine nucleoside phosphorylase deficiency is a rare autosomal recessive immunodeficiency disorder characterized mainly by decreased T-cell function. Some patients also have neurologic impairment (review by Aust et al., 1992).

Congenital disorder of glycosylation type IIc (CDG2C) is an autosomal recessive disorder characterized by moderate to severe psychomotor retardation, mild dysmorphism, and impaired neutrophil motility. It is a member of a group of disorders with a defect in the processing of protein-bound glycans. For a general overview of congenital disorders of glycosylation (CDGs), see CDG1A (212065) and CDG2A (212066). Frydman (1996) contended that the neutrophil defect in CDG2C, which has been referred to as 'leukocyte adhesion deficiency type II' (LAD2), is a manifestation of the disorder and that there are no cases of 'primary' LAD II. Etzioni and Harlan (1999) provided a comprehensive review of both leukocyte adhesion deficiency-1 (LAD1; 116920) and LAD2. While the functional neutrophil studies are similar in the 2 LADs, the clinical course is milder in LAD2. Furthermore, patients with LAD2 present other abnormal features, such as growth and mental retardation, which are related to the primary defect in fucose metabolism. Delayed separation of the umbilical cord occurs in LAD1. For a discussion of genetic heterogeneity of LAD, see 116920.

Wiedemann-Rautenstrauch syndrome (WDRTS) is a rare autosomal recessive neonatal progeroid disorder characterized by intrauterine growth retardation, failure to thrive, short stature, a progeroid appearance, hypotonia, and variable mental impairment (summary by Toriello, 1990). Average survival in WDRTS is 7 months, although survival into the third decade of life has been reported (Akawi et al., 2013).

A subtype of autosomal recessive limb-girdle muscular dystrophy characterized by a childhood onset of progressive shoulder and pelvic girdle muscle weakness and atrophy frequently associated with calf hypertrophy, diaphragmatic weakness, and/or variable cardiac abnormalities. Mild to moderate elevated serum creatine kinase levels and positive Gowers sign are reported.

IGHD3 is characterized by agammaglobulinemia and markedly reduced numbers of B cells, short stature, delayed bone age, and good response to treatment with growth hormone (summary by Conley et al., 1991). For general phenotypic information and a discussion of genetic heterogeneity of IGHD, see 262400.

Hereditary mucoepithelial dysplasia (HMD) is a rare autosomal dominant genodermatosis characterized by onset in infancy of a panepithelial defect involving the oral, nasal, conjunctival, vaginal, cervical, perineal, urethral, and bladder mucosa. Patients develop cataracts, blindness, nonscarring alopecia, perineal psoriasiform lesions, and follicular keratoses (Witkop et al., 1982). Although 1 family was reported to have progressive severe interstitial lung disease (Witkop et al., 1979), this feature has not been reported in other families and is not considered a criterion for diagnosis. However, the clinical triad of nonscarring alopecia, well-demarcated fiery red mucosa, and psoriasiform perineal involvement has been consistently observed (review by Boralevi et al., 2005).

The phenotypic spectrum of X-linked severe combined immunodeficiency (X-SCID) ranges from typical X-SCID (early-onset disease in males that is fatal if not treated with hematopoietic stem cell transplantation [HSCT] or gene therapy) to atypical X-SCID (later-onset disease comprising phenotypes caused by variable immunodeficiency, immune dysregulation, and/or autoimmunity). Typical X-SCID. Prior to universal newborn screening (NBS) for SCID most males with typical X-SCID came to medical attention between ages three and six months because of recurrent infections, persistent infections, and infections with opportunistic organisms. With universal NBS for SCID, the common presentation for typical X-SCID is now an asymptomatic, healthy-appearing male infant. Atypical X-SCID, which usually is not detected by NBS, can manifest in the first years of life or later with one of the following: recurrent upper and lower respiratory tract infections with bronchiectasis; Omenn syndrome, a clinical phenotype caused by immune dysregulation; X-SCID combined immunodeficiency (often with recurrent infections, warts, and dermatitis); immune dysregulation and autoimmunity; or Epstein-Barr virus-related lymphoproliferative complications.

Severe combined immunodeficiency refers to a genetically and clinically heterogeneous group of disorders with defective cellular and humoral immune function. Patients with SCID present in infancy with recurrent, persistent infections by opportunistic organisms, including Candida albicans, Pneumocystis carinii, and cytomegalovirus, among many others. Laboratory analysis shows profound lymphopenia with diminished or absent immunoglobulins. The common characteristic of all types of SCID is absence of T cell-mediated cellular immunity due to a defect in T-cell development. Without treatment, patients usually die within the first year of life. The overall prevalence of all types of SCID is approximately 1 in 75,000 births (Fischer et al., 1997; Buckley, 2004). Genetic Heterogeneity of SCID SCID can be divided into 2 main classes: those with B lymphocytes (B+ SCID) and those without (B- SCID). Presence or absence of NK cells is variable within these groups. The most common form of SCID is X-linked T-, B+, NK- SCID (SCIDX1; 300400) caused by mutation in the IL2RG gene (308380) on chromosome Xq13.1. Autosomal recessive SCID includes T-, B-, NK+ SCID, caused by mutation in the RAG1 and RAG2 genes on 11p13; T-, B+, NK- SCID (600802), caused by mutation in the JAK3 gene (600173) on 19p13; T-, B+, NK+ SCID (IMD104; 608971), caused by mutation in the IL7R gene (146661) on 5p13; T-, B+, NK+ SCID (IMD105; 619924), caused by mutation in the CD45 gene (PTPRC; 151460) on 1q31-q32; T-, B+, NK+ SCID (IMD19; 615617), caused by mutation in the CD3D gene (186790) on 11q23; T-, B-, NK- SCID (102700) caused by mutation in the ADA (608958) gene on 20q13; and T-, B-, NK+ SCID with sensitivity to ionizing radiation (602450), caused by mutation in the Artemis gene (DCLRE1C; 605988) on 10p13 (Kalman et al., 2004); and T-, B-, NK+ SCID with microcephaly, growth retardation, and sensitivity to ionizing radiation (611291), caused by mutation in the NHEJ1 gene (611290) on 2q35. Approximately 20 to 30% of all SCID patients are T-, B-, NK+, and approximately half of these patients have mutations in the RAG1 or RAG2 genes (Schwarz et al., 1996; Fischer et al., 1997).

The first identified CACNA1C-related disorder, referred to as Timothy syndrome, consists of the combination of prolonged QT interval, autism, and cardiovascular malformation with syndactyly of the fingers and toes. Infrequent findings also include developmental and speech delay, seizures, and recurrent infections. With increased availability of molecular genetic testing, a wider spectrum of pathogenic variants and clinical findings associated with CACNA1C-related disorders has been recognized. Because CACNA1C is associated with calcium channel function, all individuals with a pathogenic variant in this gene are at risk for cardiac arrhythmia of a specific type. The clinical manifestations of a CACNA1C-related disorder include three phenotypes: Timothy syndrome with or without syndactyly. QT prolongation (QTc >480 ms) and arrhythmias in the absence of other syndromic features. Short QT syndrome (QTc <350 ms) or Brugada syndrome with short QT interval. These three phenotypes can be separated into two broad categories on the basis of the functional consequences of the pathogenic variants in CACNA1C: QT prolongation with or without a Timothy syndrome-associated phenotype associated with pathogenic variants inducing a gain of function at the cellular level (i.e., increased calcium current). Short QT interval with or without Brugada syndrome EKG pattern associated with pathogenic variants causing loss of function (i.e., reduced calcium current).

JAK3-deficient severe combined immunodeficiency (SCID) is an inherited disorder of the immune system. Individuals with JAK3-deficient SCID lack the necessary immune cells to fight off certain bacteria, viruses, and fungi. They are prone to repeated and persistent infections that can be very serious or life-threatening. Often the organisms that cause infection in people with JAK3-deficient SCID are described as opportunistic because they ordinarily do not cause illness in healthy people. Affected infants typically develop chronic diarrhea, a fungal infection in the mouth called oral thrush, pneumonia, and skin rashes. Persistent illness also causes affected individuals to grow more slowly than other children. Without treatment, people with JAK3-deficient SCID usually live only into early childhood.

Spondyloenchondrodysplasia with immune dysregulation (SPENCDI) is an immunoosseous dysplasia combining the typical metaphyseal and vertebral bone lesions of spondyloenchondrodysplasia (SPENCD) with immune dysfunction and neurologic involvement. The skeletal dysplasia is characterized by radiolucent and irregular spondylar and metaphyseal lesions that represent islands of chondroid tissue within bone. The vertebral bodies show dorsally accentuated platyspondyly with disturbance of ossification. Clinical abnormalities such as short stature, rhizomelic micromelia, increased lumbar lordosis, barrel chest, facial anomalies, and clumsy movements may be present (Menger et al., 1989). Central nervous system involvement includes spasticity, mental retardation, and cerebral calcifications, and immune dysregulation ranges from autoimmunity to immunodeficiency. Neurologic and autoimmune manifestations have been observed in different combinations within a single family, suggesting that this disorder may be defined by specific radiographic features but has remarkably pleiotropic manifestations (Renella et al., 2006). Briggs et al. (2016) also noted variability in skeletal, neurologic, and immune phenotypes, which was sometimes marked between members of the same family. Classification of the Enchondromatoses In their classification of the enchondromatoses, Spranger et al. (1978) called Ollier disease and Maffucci syndrome types I and II enchondromatosis, respectively; metachondromatosis (156250), type III; and spondyloenchondrodysplasia (SPENCD), also called spondyloenchondromatosis, type IV; enchondromatosis with irregular vertebral lesions, type V; and generalized enchondromatosis, type VI. Halal and Azouz (1991) added 3 tentative categories to the 6 in the classification of Spranger et al. (1978). Pansuriya et al. (2010) suggested a new classification of enchondromatosis (multiple enchondromas).

Caspase 8 deficiency is a syndrome of lymphadenopathy and splenomegaly, marginal elevation of 'double-negative T cells' (DNT; T-cell receptor alpha/beta+, CD4-/CD8-), defective FAS-induced apoptosis, and defective T-, B-, and natural killer (NK)-cell activation, with recurrent bacterial and viral infections (summary by Madkaikar et al., 2011).

Adenosine deaminase (ADA) deficiency is a systemic purine metabolic disorder that primarily affects lymphocyte development, viability, and function. The clinical phenotypic spectrum includes: Severe combined immunodeficiency disease (SCID), often diagnosed by age six months and usually by age 12 months; Less severe "delayed" onset combined immune deficiency (CID), usually diagnosed between age one and ten years; "Late/adult onset" CID, diagnosed in the second to fourth decades; Benign "partial ADA deficiency" (very low or absent ADA activity in erythrocytes but greater ADA activity in nucleated cells), which is compatible with normal immune function. Infants with typical early-onset ADA-deficient SCID have failure to thrive and opportunistic infections associated with marked depletion of T, B, and NK lymphocytes, and an absence of both humoral and cellular immune function. If immune function is not restored, children with ADA-deficient SCID rarely survive beyond age one to two years. Infections in delayed- and late-onset types (commonly, recurrent otitis, sinusitis, and upper respiratory) may initially be less severe than those in individuals with ADA-deficient SCID; however, by the time of diagnosis these individuals often have chronic pulmonary insufficiency and may have autoimmune phenomena (cytopenias, anti-thyroid antibodies), allergies, and elevated serum concentration of IgE. The longer the disorder goes unrecognized, the more immune function deteriorates and the more likely are chronic sequelae of recurrent infection.

Severe combined immunodeficiency (SCID) due to DCLRE1C deficiency is a type of SCID (see this term) characterized by severe and recurrent infections, diarrhea, failure to thrive, and cell sensitivity to ionizing radiation.

Pulmonary alveolar proteinosis is a pathologic entity characterized by intraalveolar surfactant accumulation. There are 3 clinically distinct forms: hereditary (usually congenital), secondary, and acquired. The acquired form of pulmonary alveolar proteinosis is the most common form, accounting for approximately 90% of cases. The mean age at diagnosis is 39 years and it is associated with smoking in 72% of cases. The estimated incidence and prevalence are 0.36 and 3.70 cases per million, respectively (Trapnell et al., 2003; Seymour and Presneill, 2002). Secondary pulmonary alveolar proteinosis develops in association with conditions involving functional impairment or reduced numbers of alveolar macrophages. Such conditions include some hematologic cancers, pharmacologic immunosuppression, inhalation of inorganic dust or toxic fumes, and certain infections. Congenital pulmonary alveolar proteinosis is a rare, severe, often fatal disorder of newborns associated with pulmonary surfactant metabolism dysfunction caused by mutations in genes involved in surfactant metabolism (see, e.g., SMDP1, 265120) (Trapnell et al., 2003). See 300770 for information on congenital PAP due to CSF2RA (306250) deficiency.

Acute necrotizing encephalopathy type 1, also known as susceptibility to infection-induced acute encephalopathy 3 or IIAE3, is a rare type of brain disease (encephalopathy) that occurs following a viral infection such as the flu.\n\nAcute necrotizing encephalopathy type 1 typically appears in infancy or early childhood, although some people do not develop the condition until adolescence or adulthood. People with this condition usually show typical symptoms of an infection, such as fever, cough, congestion, vomiting, and diarrhea, for a few days. Following these flu-like symptoms, affected individuals develop neurological problems, such as seizures, hallucinations, difficulty coordinating movements (ataxia), or abnormal muscle tone. Eventually, most affected individuals go into a coma, which usually lasts for a number of weeks. The condition is described as "acute" because the episodes of illness are time-limited.\n\nPeople with acute necrotizing encephalopathy type 1 develop areas of damage (lesions) in certain regions of the brain. As the condition progresses, these brain regions develop swelling (edema), bleeding (hemorrhage), and then tissue death (necrosis). The progressive brain damage and tissue loss results in encephalopathy.\n\nApproximately one-third of individuals with acute necrotizing encephalopathy type 1 do not survive their illness and subsequent neurological decline. Of those who do survive, about half have permanent brain damage due to tissue necrosis, resulting in impairments in walking, speech, and other basic functions. Over time, many of these skills may be regained, but the loss of brain tissue is permanent. Other individuals who survive their illness appear to recover completely.\n\nIt is estimated that half of individuals with acute necrotizing encephalopathy type 1 are susceptible to recurrent episodes and will have another infection that results in neurological decline; some people may have numerous episodes throughout their lives. Neurological function worsens following each episode as more brain tissue is damaged.

Primary ciliary dyskinesia is an autosomal recessive disorder resulting from loss of normal ciliary function. Kartagener (pronounced KART-agayner) syndrome is characterized by the combination of primary ciliary dyskinesia and situs inversus, and occurs in approximately half of patients with ciliary dyskinesia. Since normal nodal ciliary movement in the embryo is required for normal visceral asymmetry, absence of normal ciliary movement results in a lack of definitive patterning; thus, random chance alone appears to determine whether the viscera take up the normal or reversed left-right position during embryogenesis. This explains why approximately 50% of patients, even within the same family, have situs inversus (Afzelius, 1976; El Zein et al., 2003). For a general description and a discussion of genetic heterogeneity of primary ciliary dyskinesia and Kartagener syndrome, see CILD1 (244400).

Omenn syndrome is an autosomal recessive disorder characterized by severe combined immunodeficiency (SCID) associated with erythrodermia, hepatosplenomegaly, lymphadenopathy, and alopecia. B cells are mostly absent, T-cell counts are normal to elevated, and T cells are frequently activated and express a restricted T-cell receptor (TCR) repertoire (summary by Ege et al., 2005). Another distinct form of familial histiocytic reticulocytosis (267700) is caused by mutation in the perforin-1 gene (PRF1; 170280) on chromosome 10q22.

Roifman-Chitayat syndrome (ROCHIS) is an autosomal recessive digenic disorder characterized by global developmental delay, variable neurologic features such as seizures, ataxia, and optic atrophy, dysmorphic facial features, distal skeletal anomalies, and combined immunodeficiency manifest as recurrent infections (summary by Sharfe et al., 2018).

Common variable immunodeficiency (CVID) is a clinically and genetically heterogeneous group of disorders characterized by antibody deficiency, hypogammaglobulinemia, recurrent bacterial infections, and an inability to mount an antibody response to antigen. The defect results from a failure of B-cell differentiation and impaired secretion of immunoglobulins; the numbers of circulating B cells are usually in the normal range, but can be low. Most individuals with CVID have onset of infections after age 10 years. CVID represents the most common form of primary immunodeficiency disorders and is the most common form of primary antibody deficiency. Approximately 10 to 20% of patients with a diagnosis of CVID have a family history of the disorder (reviews by Chapel et al., 2008, Conley et al., 2009, and Yong et al., 2009). Genetic Heterogeneity of Common Variable Immunodeficiency Common variable immunodeficiency is a genetically heterogeneous disorder. See also CVID2 (240500), caused by mutation in the TACI gene (TNFRSF13B; 604907); CVID3 (613493), caused by mutation in the CD19 gene (107265); CVID4 (613494), caused by mutation in the BAFFR gene (TNFRSF13C; 606269); CVID5 (613495), caused by mutation in the CD20 gene (112210); CVID6 (613496), caused by mutation in the CD81 gene (186845); CVID7 (614699), caused by mutation in the CD21 gene (CR2; 120650); CVID8 (614700), caused by mutation in the LRBA gene (606453); CVID10 (615577), caused by mutation in the NFKB2 gene (164012); CVID11 (615767), caused by mutation in the IL21 gene (605384); CVID12 (616576), caused by mutation in the NFKB1 gene (164011); CVID13 (616873), caused by mutation in the IKZF1 gene (603023); CVID14 (617765), caused by mutation in the IRF2BP2 gene (615332); and CVID15 (620670), caused by heterozygous mutation in the SEC61A1 gene (609213). The disorder formerly designated CVID9 has been found to be a form of autoimmune lymphoproliferative disorder; see ALPS3 (615559).

Immunodeficiency, centromeric instability, and facial dysmorphism (ICF) syndrome is a rare autosomal recessive disorder characterized by facial dysmorphism, immunoglobulin deficiency resulting in recurrent infections, and mental retardation. Laboratory studies of patient cells show hypomethylation of satellite regions of chromosomes 1, 9, and 16, as well as pericentromeric chromosomal instability in response to phytohemagglutinin stimulation (summary by de Greef et al., 2011). For a discussion of genetic heterogeneity of immunodeficiency-centromeric instability-facial anomalies syndrome, see ICF1 (242860).

Fanconi anemia (FA) is characterized by physical abnormalities, bone marrow failure, and increased risk for malignancy. Physical abnormalities, present in approximately 75% of affected individuals, include one or more of the following: short stature, abnormal skin pigmentation, skeletal malformations of the upper and/or lower limbs, microcephaly, and ophthalmic and genitourinary tract anomalies. Progressive bone marrow failure with pancytopenia typically presents in the first decade, often initially with thrombocytopenia or leukopenia. The incidence of acute myeloid leukemia is 13% by age 50 years. Solid tumors – particularly of the head and neck, skin, and genitourinary tract – are more common in individuals with FA.

Common variable immunodeficiency-8 with autoimmunity is an autosomal recessive disorder of immune dysregulation. Affected individuals have early childhood onset of recurrent infections, particularly respiratory infections, and also develop variable autoimmune disorders, including idiopathic thrombocytopenic purpura, autoimmune hemolytic anemia, and inflammatory bowel disease. The presentation and phenotype are highly variable, even within families (summary by Lopez-Herrera et al., 2012 and Alangari et al., 2012). Immunologic findings are also variable and may include decreased B cells, hypogammaglobulinemia, and deficiency of CD4+ T regulatory (Treg) cells (Charbonnier et al., 2015). For a general description and a discussion of genetic heterogeneity of common variable immunodeficiency, see CVID1 (607594).

Most characteristically, Aicardi-Goutières syndrome (AGS) manifests as an early-onset encephalopathy that usually, but not always, results in severe intellectual and physical disability. A subgroup of infants with AGS present at birth with abnormal neurologic findings, hepatosplenomegaly, elevated liver enzymes, and thrombocytopenia, a picture highly suggestive of congenital infection. Otherwise, most affected infants present at variable times after the first few weeks of life, frequently after a period of apparently normal development. Typically, they demonstrate the subacute onset of a severe encephalopathy characterized by extreme irritability, intermittent sterile pyrexias, loss of skills, and slowing of head growth. Over time, as many as 40% develop chilblain skin lesions on the fingers, toes, and ears. It is becoming apparent that atypical, sometimes milder, cases of AGS exist, and thus the true extent of the phenotype associated with pathogenic variants in the AGS-related genes is not yet known.

Immunodeficiency-27A (IMD27A) results from autosomal recessive (AR) IFNGR1 deficiency. Patients with complete IFNGR1 deficiency have a severe clinical phenotype characterized by early and often fatal mycobacterial infections. The disorder can thus be categorized as a form of mendelian susceptibility to mycobacterial disease (MSMD). Bacillus Calmette-Guerin (BCG) and environmental mycobacteria are the most frequent pathogens, and infection typically begins before the age of 3 years. Plasma from patients with complete AR IFNGR1 deficiency usually contains large amounts of IFNG (147570), and their cells do not respond to IFNG in vitro. In contrast, cells from patients with partial AR IFNGR1 deficiency, which is caused by a specific mutation in IFNGR1, retain residual responses to high IFNG concentrations. Patients with partial AR IFNGR1 deficiency are susceptible to BCG and environmental mycobacteria, but they have a milder clinical disease and better prognosis than patients with complete AR IFNGR1 deficiency. The clinical features of children with complete AR IFNGR1 deficiency are usually more severe than those in individuals with AD IFNGR1 deficiency (IMD27B), and mycobacterial infection often occurs earlier (mean age of 1.3 years vs 13.4 years), with patients having shorter mean disease-free survival. Salmonellosis is present in about 5% of patients with AR or AD IFNGR1 deficiency, and other infections have been reported in single patients (review by Al-Muhsen and Casanova, 2008).

Immunodeficiency-32B is an autosomal recessive primary immunodeficiency characterized by recurrent infections resulting from variable defects in immune cell development or function, including monocytes, dendritic cells, and natural killer (NK) cells. Patients have particular susceptibility to viral disease (summary by Mace et al., 2017).

Immunodeficiency-51 (IMD51) is an autosomal recessive primary immune deficiency that is usually characterized by onset of chronic mucocutaneous candidiasis in the first years of life. Most patients also show recurrent Staphylococcal skin infections, and may show increased susceptibility to chronic bacterial respiratory infections. Patient cells show a lack of cellular responses to stimulation with certain IL17 isoforms, including IL17A (603149), IL17F (606496), IL17A/F, and IL17E (IL25; 605658) (summary by Levy et al., 2016).

IMD11B is an autosomal dominant disorder of immune dysfunction characterized by onset of moderate to severe atopic dermatitis in early childhood. Some patients may have recurrent infections and other variable immune abnormalities. Laboratory studies show defects in T-cell activation, increased IgE, and eosinophilia (summary by Ma et al., 2017).

Geleophysic dysplasia, a progressive condition resembling a lysosomal storage disorder, is characterized by short stature, short hands and feet, progressive joint limitation and contractures, distinctive facial features, progressive cardiac valvular disease, and thickened skin. Intellect is normal. Major findings are likely to be present in the first year of life. Cardiac, respiratory, and lung involvement result in death before age five years in approximately 33% of individuals with ADAMTSL2-related geleophysic dysplasia.

Immunodeficiency, centromeric instability, and facial dysmorphism (ICF) syndrome is a rare autosomal recessive disease characterized by facial dysmorphism, immunoglobulin deficiency, and branching of chromosomes 1, 9, and 16 after phytohemagglutinin (PHA) stimulation of lymphocytes. Hypomethylation of DNA of a small fraction of the genome is an unusual feature of ICF patients that is explained by mutations in the DNMT3B gene in some, but not all, ICF patients (Hagleitner et al., 2008). Genetic Heterogeneity of Immunodeficiency-Centromeric Instability-Facial Anomalies Syndrome See also ICF2 (614069), caused by mutation in the ZBTB24 gene (614064) on chromosome 6q21; ICF3 (616910), caused by mutation in the CDCA7 gene (609937) on chromosome 2q31; and ICF4 (616911), caused by mutation in the HELLS gene (603946) on chromosome 10q23.

Cornelia de Lange syndrome (CdLS) encompasses a spectrum of findings from mild to severe. Severe (classic) CdLS is characterized by distinctive facial features, growth restriction (prenatal onset; <5th centile throughout life), hypertrichosis, and upper-limb reduction defects that range from subtle phalangeal abnormalities to oligodactyly (missing digits). Craniofacial features include synophrys, highly arched and/or thick eyebrows, long eyelashes, short nasal bridge with anteverted nares, small widely spaced teeth, and microcephaly. Individuals with a milder phenotype have less severe growth, cognitive, and limb involvement, but often have facial features consistent with CdLS. Across the CdLS spectrum IQ ranges from below 30 to 102 (mean: 53). Many individuals demonstrate autistic and self-destructive tendencies. Other frequent findings include cardiac septal defects, gastrointestinal dysfunction, hearing loss, myopia, and cryptorchidism or hypoplastic genitalia.

Primary ciliary dyskinesia is a genetically heterogeneous autosomal recessive disorder resulting from loss of function of different parts of the primary ciliary apparatus, most often dynein arms. Kartagener (pronounced KART-agayner) syndrome is characterized by the combination of primary ciliary dyskinesia and situs inversus (270100), and occurs in approximately half of patients with ciliary dyskinesia. Since normal nodal ciliary movement in the embryo is required for normal visceral asymmetry, absence of normal ciliary movement results in a lack of definitive patterning; thus, random chance alone appears to determine whether the viscera take up the normal or reversed left-right position during embryogenesis. This explains why approximately 50% of patients, even within the same family, have situs inversus (Afzelius, 1976; El Zein et al., 2003). Genetic Heterogeneity of Primary Ciliary Dyskinesia Other forms of primary ciliary dyskinesia include CILD2 (606763), caused by mutation in the DNAAF3 gene (614566) on 19q13; CILD3 (608644), caused by mutation in the DNAH5 gene (603335) on 5p15; CILD4 (608646), mapped to 15q13; CILD5 (608647), caused by mutation in the HYDIN gene (610812) on 16q22; CILD6 (610852), caused by mutation in the TXNDC3 gene (607421) on 7p14; CILD7 (611884), caused by mutation in the DNAH11 gene (603339) on 7p15; CILD8 (612274), mapped to 15q24-q25; CILD9 (612444), caused by mutation in the DNAI2 gene (605483) on 17q25; CILD10 (612518), caused by mutation in the DNAAF2 gene (612517) on 14q21; CILD11 (612649), caused by mutation in the RSPH4A gene (612647) on 6q22; CILD12 (612650), caused by mutation in the RSPH9 gene (612648) on 6p21; CILD13 (613193), caused by mutation in the DNAAF1 gene (613190) on 16q24; CILD14 (613807), caused by mutation in the CCDC39 gene (613798) gene on 3q26; CILD15 (613808), caused by mutation in the CCDC40 gene (613799) on 17q25; CILD16 (614017), caused by mutation in the DNAL1 gene (610062) on 14q24; CILD17 (614679), caused by mutation in the CCDC103 gene (614677) on 17q21; CILD18 (614874), caused by mutation in the DNAAF5 gene (614864) on 7p22; CILD19 (614935), caused by mutation in the LRRC6 gene (614930) on 8q24; CILD20 (615067), caused by mutation in the CCDC114 gene (615038) on 19q13; CILD21 (615294), caused by mutation in the DRC1 gene (615288) on 2p23; CILD22 (615444), caused by mutation in the ZMYND10 gene (607070) on 3p21; CILD23 (615451), caused by mutation in the ARMC4 gene (615408) on 10p; CILD24 (615481), caused by mutation in the RSPH1 gene (609314) on 21q22; CILD25 (615482), caused by mutation in the DYX1C1 gene (608706) on 15q21; CILD26 (615500), caused by mutation in the C21ORF59 gene (615494) on 21q22; CILD27 (615504), caused by mutation in the CCDC65 gene (611088) on 12q13; CILD28 (615505), caused by mutation in the SPAG1 gene (603395) on 8q22; CILD29 (615872), caused by mutation in the CCNO gene (607752) on 5q11; CILD30 (616037), caused by mutation in the CCDC151 gene (615956) on 19p13; CILD32 (616481), caused by mutation in the RSPH3 gene (615876) on 6q25; CILD33 (616726), caused by mutation in the GAS8 gene (605178) on 16q24; CILD34 (617091), caused by mutation in the DNAJB13 gene (610263) on 11q13; CILD35 (617092), caused by mutation in the TTC25 gene (617095) on 17q21; CILD36 (300991), caused by mutation in the PIH1D3 gene (300933) on Xq22; CILD37 (617577), caused by mutation in the DNAH1 gene (603332) on 3p21; CILD38 (618063), caused by mutation in the CFAP300 gene (618058) on 11q22; CILD39 (618254), caused by mutation in the LRRC56 gene (618227) on 11p15; CILD40 (618300), caused by mutation in the DNAH9 gene (603330) on 17p12; CILD41 (618449), caused by mutation in the GAS2L2 gene (611398) on 17q12; CILD42 (618695), caused by mutation in the MCIDAS gene (614086) on 5q11; CILD43 (618699), caused by mutation in the FOXJ1 gene (602291) on 17q25; CILD44 (618781), caused by mutation in the NEK10 gene (618726) on 3p24; CILD45 (618801), caused by mutation in the TTC12 gene (610732) on 11q23; CILD46 (619436), caused by mutation in the STK36 gene (607652) on 2q35; CILD47 (619466), caused by mutation in the TP73 gene (601990) on 1p36; CILD48 (620032), caused by mutation in the NME5 gene (603575) on chromosome 5q31; CILD49 (620197), caused by mutation in the CFAP74 gene (620187) on chromosome 1p36; CILD50 (620356), caused by mutation in the DNAH7 gene (610061) on chromosome 2q32; CILD51 (620438), caused by mutation in the BRWD1 gene (617824) on chromosome 21q22; CILD52 (620570), caused by mutation in the DAW1 gene (620279) on chromosome 2q36; and CILD53 (620642), caused by mutation in the CLXN gene (619564) on chromosome 8q11. Ciliary abnormalities have also been reported in association with both X-linked and autosomal forms of retinitis pigmentosa. Mutations in the RPGR gene (312610), which underlie X-linked retinitis pigmentosa (RP3; 300029), are in some instances (e.g., 312610.0016) associated with recurrent respiratory infections indistinguishable from immotile cilia syndrome; see 300455. Afzelius (1979) gave an extensive review of cilia and their disorders. There are also several possibly distinct CILDs described based on the electron microscopic appearance of abnormal cilia, including CILD with transposition of the microtubules (215520), CILD with excessively long cilia (242680), and CILD with defective radial spokes (242670).

Primary ciliary dyskinesia-42 (CILD42) is an autosomal recessive disorder characterized by a defect in motile cilia and ciliary clearance resulting in the onset of respiratory insufficiency soon after birth, and associated with recurrent upper and lower respiratory infections with chronic progressive lung disease. Other more variable features may include infertility and mild hydrocephalus. Patients with this form of the disorder do not have situs abnormalities. The disorder is considered to be a type of ciliopathy known as 'reduced generation of multiple motile cilia' (RGMC) (summary by Boon et al., 2014). For a discussion of genetic heterogeneity of primary ciliary dyskinesia, CILD1 (244400).

Infantile T-cell lymphopenia with or without nail dystrophy (TLIND) is an autosomal dominant disorder characterized by decreased numbers of T cells, particularly cytotoxic CD8+ T cells, usually apparent from infancy. Patients are often identified through newborn screening with the finding of low levels of T-cell receptor excision circles (TRECs). Affected individuals tend to be more susceptible to recurrent infections, mainly respiratory viral infections. However, the severity is highly variable, and patients usually improve with age later in childhood and as adults, even if CD8+ T cells remain decreased compared to normal. Additional features may include a small thymic shadow, indicative of impaired thymic development, skin abnormalities, such as atopic dermatitis, and nail dystrophy. As rare patients may develop more serious infections, affected individuals should be monitored. Bone marrow transplantation is not curative (summary by Bosticardo et al., 2019).

Immunodeficiency-82 with systemic inflammation (IMD82) is a complex autosomal dominant immunologic disorder characterized by recurrent infections with various organisms, as well as noninfectious inflammation manifest as lymphocytic organ infiltration with gastritis, colitis, and lung, liver, CNS, or skin disease. One of the more common features is inflammation of the stomach and bowel. Most patients develop symptoms in infancy or early childhood; the severity is variable. There may be accompanying fever, elevated white blood cell count, decreased B cells, hypogammaglobulinemia, increased C-reactive protein (CRP; 123260), and a generalized hyperinflammatory state. Immunologic workup shows variable B- and T-cell abnormalities such as skewed subgroups. Patients have a propensity for the development of lymphoma, usually in adulthood. At the molecular level, the disorder results from a gain-of-function mutation that leads to constitutive and enhanced activation of the intracellular inflammatory signaling pathway. Treatment with SYK inhibitors rescued human cell abnormalities and resulted in clinical improvement in mice (Wang et al., 2021).

DEGCAGS syndrome is an autosomal recessive syndromic neurodevelopmental disorder characterized by global developmental delay, coarse and dysmorphic facial features, and poor growth and feeding apparent from infancy. Affected individuals have variable systemic manifestations often with significant structural defects of the cardiovascular, genitourinary, gastrointestinal, and/or skeletal systems. Additional features may include sensorineural hearing loss, hypotonia, anemia or pancytopenia, and immunodeficiency with recurrent infections. Death in childhood may occur (summary by Bertoli-Avella et al., 2021).

Immunodeficiency-92 (IMD92) is an autosomal recessive primary immunodeficiency characterized by the onset of recurrent infections in infancy or early childhood. Infectious agents are broad, including bacterial, viral, fungal, and parasitic, including Cryptosporidium and Mycobacteria. Patient lymphocytes show defects in both T- and B-cell proliferation, cytokine secretion, and overall function, and there is also evidence of dysfunction of NK, certain antigen-presenting cells, and myeloid subsets. Hematopoietic stem cell transplantation may be curative (summary by Beaussant-Cohen et al., 2019 and Levy et al., 2021).

ZAP70-related combined immunodeficiency (ZAP70-related CID) is a cell-mediated immunodeficiency caused by abnormal T-cell receptor (TCR) signaling. Affected children usually present in the first year of life with recurrent bacterial, viral, and opportunistic infections, diarrhea, and failure to thrive. Severe lower-respiratory infections and oral candidiasis are common. Affected children usually do not survive past their second year without hematopoietic stem cell transplantation (HSCT).

Immunodeficiency-104 (IMD104) is an autosomal recessive disorder characterized by the onset of recurrent infections in early infancy. Manifestations may include oral thrush, fever, and failure to thrive. Some patients have lymphadenopathy and hepatosplenomegaly, whereas others have absence of lymph nodes and lack a thymic shadow. Laboratory studies show decreased or absent numbers of nonfunctional T cells, normal or increased levels of B cells, variable hypogammaglobulinemia, and normal NK cells. The disorder is caused by a defect in IL7 (146660) signaling due to a mutant IL7 receptor. Hematopoietic stem cell transplantation may be curative (Roifman et al., 2000 and Giliani et al., 2005). Giliani et al. (2005) provided a detailed review of IL7R deficiency, including discussion of the IL7R gene and its function in the immune system, clinical features of the disorder, and experiences with hematopoietic stem cell transplant as treatment. For a general phenotypic description and a discussion of genetic heterogeneity of autosomal recessive SCID, see 601457.

Severe congenital liver disease (SCOLIV) is an autosomal recessive disorder characterized by the onset of progressive hepatic dysfunction usually in the first years of life. Affected individuals show feeding difficulties with failure to thrive and features such as jaundice, hepatomegaly, and abdominal distension. Laboratory workup is consistent with hepatic insufficiency and may also show coagulation defects, anemia, or metabolic disturbances. Cirrhosis and hypernodularity are commonly observed on liver biopsy. Many patients die of liver failure in early childhood (Moreno Traspas et al., 2022).