MedGen

Down syndrome, the most frequent form of mental retardation caused by a microscopically demonstrable chromosomal aberration, is characterized by well-defined and distinctive phenotypic features and natural history. It is caused by triplicate state (trisomy) of all or a critical portion of chromosome 21. [from OMIM]

CHD7 disorder encompasses the entire phenotypic spectrum of heterozygous CHD7 pathogenic variants that includes CHARGE syndrome as well as subsets of features that comprise the CHARGE syndrome phenotype. The mnemonic CHARGE syndrome, introduced in the premolecular era, stands for coloboma, heart defect, choanal atresia, retarded growth and development, genital hypoplasia, ear anomalies (including deafness). Following the identification of the genetic cause of CHD7 disorder, the phenotypic spectrum expanded to include cranial nerve anomalies, vestibular defects, cleft lip and/or palate, hypothyroidism, tracheoesophageal anomalies, brain anomalies, seizures, and renal anomalies. Life expectancy highly depends on the severity of manifestations; mortality can be high in the first few years when severe birth defects (particularly complex heart defects) are present and often complicated by airway and feeding issues. In childhood, adolescence, and adulthood, decreased life expectancy is likely related to a combination of residual heart defects, infections, aspiration or choking, respiratory issues including obstructive and central apnea, and possibly seizures. Despite these complications, the life expectancy for many individuals can be normal. [from GeneReviews]

Oculofaciocardiodental (OFCD) syndrome is a condition that affects the development of the eyes (oculo-), facial features (facio-), heart (cardio-) and teeth (dental). This condition occurs only in females.

The eye abnormalities associated with OFCD syndrome can affect one or both eyes. Many people with this condition are born with eyeballs that are abnormally small (microphthalmia). Other eye problems can include clouding of the lens (cataract) and a higher risk of glaucoma, an eye disease that increases the pressure in the eye. These abnormalities can lead to vision loss or blindness.

People with OFCD syndrome often have a long, narrow face with distinctive facial features, including deep-set eyes and a broad nasal tip that is divided by a cleft. Some affected people have an opening in the roof of the mouth called a cleft palate.

Heart defects are another common feature of OFCD syndrome. Babies with this condition may be born with a hole between two chambers of the heart (an atrial or ventricular septal defect) or a leak in one of the valves that controls blood flow through the heart (mitral valve prolapse).

Teeth with very large roots (radiculomegaly) are characteristic of OFCD syndrome. Additional dental abnormalities can include delayed loss of primary (baby) teeth, missing or abnormally small teeth, misaligned teeth, and defective tooth enamel. [from MedlinePlus Genetics]

An autosomal dominant form of bicuspid aortic valve caused by mutation(s) in the NOTCH1 gene, encoding neurogenic locus notch homolog protein 1. [from NCI]

A group of congenital cardiac outflow tract anomalies that include such defects as tetralogy of Fallot, pulmonary atresia with ventricular septal defect, double-outlet right ventricle (DORV), double-outlet left ventricle, truncus arteriosus and transposition of the great arteries (TGA), among others. This group of defects is frequently found in patients with 22q11.2 deletion syndrome . A deletion of chromosome 22q11.2 has equally been associated in a subset of patients with various types of isolated non-syndromic conotruncal heart malformations (with the exception of DORV and TGA where this is very uncommon). [from ORDO]

Heterotaxy Heterotaxy ('heter' meaning 'other' and 'taxy' meaning 'arrangement'), or situs ambiguus, is a developmental condition characterized by randomization of the placement of visceral organs, including the heart, lungs, liver, spleen, and stomach. The organs are oriented randomly with respect to the left-right axis and with respect to one another (Srivastava, 1997). Heterotaxy is a clinically and genetically heterogeneous disorder. Multiple Types of Congenital Heart Defects Congenital heart defects (CHTD) are among the most common congenital defects, occurring with an incidence of 8/1,000 live births. The etiology of CHTD is complex, with contributions from environmental exposure, chromosomal abnormalities, and gene defects. Some patients with CHTD also have cardiac arrhythmias, which may be due to the anatomic defect itself or to surgical interventions (summary by van de Meerakker et al., 2011). Reviews Obler et al. (2008) reviewed published cases of double-outlet right ventricle and discussed etiology and associations. Genetic Heterogeneity of Visceral Heterotaxy See also HTX2 (605376), caused by mutation in the CFC1 gene (605194) on chromosome 2q21; HTX3 (606325), which maps to chromosome 6q21; HTX4 (613751), caused by mutation in the ACVR2B gene (602730) on chromosome 3p22; HTX5 (270100), caused by mutation in the NODAL gene (601265) on chromosome 10q22; HTX6 (614779), caused by mutation in the CCDC11 gene (614759) on chromosome 18q21; HTX7 (616749), caused by mutation in the MMP21 gene (608416) on chromosome 10q26; HTX8 (617205), caused by mutation in the PKD1L1 gene (609721) on chromosome 7p12; HTX9 (618948), caused by mutation in the MNS1 gene (610766) on chromosome 15q21; HTX10 (619607), caused by mutation in the CFAP52 gene (609804) on chromosome 17p13; HTX11 (619608), caused by mutation in the CFAP45 gene (605152) on chromosome 1q23; and HTX12 (619702), caused by mutation in the CIROP gene (619703) on chromosome 14q11. Genetic Heterogeneity of Multiple Types of Congenital Heart Defects An X-linked form of CHTD, CHTD1, is caused by mutation in the ZIC3 gene on chromosome Xq26. CHTD2 (614980) is caused by mutation in the TAB2 gene (605101) on chromosome 6q25. A form of nonsyndromic congenital heart defects associated with cardiac rhythm and conduction disturbances (CHTD3; 614954) has been mapped to chromosome 9q31. CHTD4 (615779) is caused by mutation in the NR2F2 gene (107773) on chromosome 15q26. CHTD5 (617912) is caused by mutation in the GATA5 gene (611496) on chromosome 20q13. CHTD6 (613854) is caused by mutation in the GDF1 gene (602880) on chromosome 19p13. CHTD7 (618780) is caused by mutation in the FLT4 gene (136352) on chromosome 5q35. CHTD8 (619657) is caused by mutation in the SMAD2 gene (601366) on chromosome 18q21. CHTD9 (620294) is caused by mutation in the PLXND1 gene (604282) on chromosome 3q22. [from OMIM]

CILD20 is an autosomal recessive ciliopathy characterized by infantile onset of chronic sinopulmonary infections resulting from immotile cilia and defective clearance. Patients may also have situs inversus or cardiac anomalies. Electron microscopy of respiratory epithelial cells shows absence of the outer dynein arms. Unlike other forms of CILD, patients with CILD20 do not appear to be infertile. For a phenotypic description and a discussion of genetic heterogeneity of primary ciliary dyskinesia, see 244400. [from OMIM]

Zellweger syndrome (ZS) is an autosomal recessive multiple congenital anomaly syndrome resulting from disordered peroxisome biogenesis. Affected children present in the newborn period with profound hypotonia, seizures, and inability to feed. Characteristic craniofacial anomalies, eye abnormalities, neuronal migration defects, hepatomegaly, and chondrodysplasia punctata are present. Children with this condition do not show any significant development and usually die in the first year of life (summary by Steinberg et al., 2006). For a complete phenotypic description and a discussion of genetic heterogeneity of Zellweger syndrome, see 214100. Individuals with PBDs of complementation group 14 (CG14, equivalent to CGJ) have mutations in the PEX19 gene. For information on the history of PBD complementation groups, see 214100. [from OMIM]

Ritscher-Schinzel syndrome (RSS) is a clinically recognizable condition that includes the cardinal findings of craniofacial features, cerebellar defects, and cardiovascular malformations resulting in the alternate diagnostic name of 3C syndrome. Dysmorphic facial features may include brachycephaly, hypotonic face with protruding tongue, flat appearance of the face on profile view, short midface, widely spaced eyes, downslanted palpebral fissures, low-set ears with overfolding of the upper helix, smooth or short philtrum, and high or cleft palate. Affected individuals also typically have a characteristic metacarpal phalangeal profile showing a consistent wavy pattern on hand radiographs. RSS is associated with variable degrees of developmental delay and intellectual disability. Eye anomalies and hypercholesterolemia may be variably present. [from GeneReviews]

Heterotaxy ('heter' meaning 'other' and 'taxy' meaning 'arrangement'), or situs ambiguus, is a developmental condition characterized by randomization of the placement of visceral organs, including the heart, lungs, liver, spleen, and stomach. The organs are oriented randomly with respect to the left-right axis and with respect to one another (Srivastava, 1997). Heterotaxy is a clinically and genetically heterogeneous disorder. For a discussion of genetic heterogeneity of visceral heterotaxy, see HTX1 (306955). [from OMIM]

The primary characteristics of the Frank-ter Haar syndrome (FTHS) are brachycephaly, wide fontanels, prominent forehead, hypertelorism, prominent eyes, macrocornea with or without glaucoma, full cheeks, small chin, bowing of the long bones, and flexion deformity of the fingers. Protruding, simple ears and prominent coccyx are also regarded as important diagnostic signs (summary by Maas et al., 2004). Borrone syndrome was described as a severe progressive multisystem disorder with features overlapping those of FTHS, including thick skin, acne conglobata, osteolysis, gingival hypertrophy, brachydactyly, camptodactyly, and mitral valve prolapse. Although it was initially thought to be a distinct phenotype, mutations in the FTHS-associated gene SH3PXD2B have been identified in patients diagnosed with Borrone syndrome. The earlier differential description was attributed to phenotypic variability as well as to differences in the ages at which patients were examined (Wilson et al., 2014). [from OMIM]

Multiple types of congenital heart defects are associated with mutation in the GDF1 gene, including tetralogy of fallot (TOF), transposition of the great arteries (TGA), double-outlet right ventricle (DORV), total anomalous pulmonary venous return (TAPVR), pulmonary stenosis or atresia, atrioventricular canal, ventricular septal defect (VSD), and hypoplastic left or right ventricle (Jin et al., 2017). For a discussion of genetic heterogeneity of multiple types of congenital heart defects, see 306955. [from OMIM]

CHIME syndrome, also known as Zunich neuroectodermal syndrome, is an extremely rare autosomal recessive multisystem disorder clinically characterized by colobomas, congenital heart defects, migratory ichthyosiform dermatosis, mental retardation, and ear anomalies (CHIME). Other clinical features include distinctive facial features, abnormal growth, genitourinary abnormalities, seizures, and feeding difficulties (summary by Ng et al., 2012). The disorder is caused by a defect in glycosylphosphatidylinositol (GPI) biosynthesis. For a discussion of genetic heterogeneity of GPI biosynthesis defects, see GPIBD1 (610293). [from OMIM]

The more common form of transposition of the great arteries, dextro-looped TGA, consists of complete inversion of the great vessels, so that the aorta incorrectly arises from the right ventricle and the pulmonary artery incorrectly arises from the left ventricle. (In the less common type of TGA, levo-looped TGA, the ventricles are inverted instead) (Goldmuntz et al., 2002). This creates completely separate pulmonary and systemic circulatory systems, an arrangement that is incompatible with life. Patients with TGA often have atrial and/or ventricular septal defects or other types of shunting that allow some mixing between the circulations in order to support life minimally, but surgical intervention is always required. For a discussion of genetic heterogeneity of dextro-looped transposition of the great arteries, see 608808. [from OMIM]

Autosomal visceral heterotaxy-8 (HTX8) is an autosomal recessive developmental disorder characterized by visceral situs inversus associated with complex congenital heart malformations caused by defects in the normal left-right asymmetric positioning of internal organs (summary by Vetrini et al., 2016). For a discussion of the genetic heterogeneity of visceral heterotaxy, see HTX1 (306955). [from OMIM]

Visceral heterotaxy-6 (HTX6) is characterized by dextrocardia with or without accompanying complex cardiovascular defects, as well as variable manifestations of visceral heterotaxy, including situs inversus totalis (Perles et al., 2012). [from OMIM]

Primary ciliary dyskinesia-39 (CILD39) is an autosomal recessive disorder characterized by chronic sinopulmonary infections beginning soon after birth and laterality defects in about 50% of patients. Although patient nasal ciliary samples have normal structure, detailed studies may show ciliary kinetic defects in some patients (summary by Bonnefoy et al., 2018). For a phenotypic description and a discussion of genetic heterogeneity of primary ciliary dyskinesia, see 244400. [from OMIM]

Vertebral, cardiac, renal, and limb defects syndrome-3 (VCRL3) is an autosomal recessive disorder characterized by severe cardiac and renal anomalies that are lethal in infancy, including hypoplastic or absent left ventricle, transposition of the great arteries, absent pulmonary trunk, and hypoplastic or absent kidneys. Patients also exhibit vertebral segmentation defects and shortening of the proximal long bones or micromelia (Szot et al., 2020). For a discussion of genetic heterogeneity of VCRL, see VCRL1 (617660). [from OMIM]

X-linked holoprosencephaly-13 (HPE13) is a neurologic disorder characterized by midline developmental defects that mainly affect the brain and craniofacial structure. The severity and manifestations are variable: some patients may have full alobar HPE with cyclopia, whereas others have semilobar HPE or septooptic dysplasia. Dysmorphic features include microcephaly, hypotelorism, low-set ears, micrognathia, and cleft lip/palate. Patients with a more severe phenotype may die in the newborn period, whereas those with a less severe phenotype show global developmental delay. Additional variable features include congenital heart defects and vertebral anomalies. Phenotypic variability may be related to the type of mutation, X-inactivation status, and possible incomplete penetrance. The STAG2 protein is part of the multiprotein cohesin complex involved in chromatid cohesion during DNA replication and transcriptional regulation; HPE13 can thus be classified as a 'cohesinopathy' (summary by Kruszka et al., 2019). For a discussion of genetic heterogeneity of holoprosencephaly, see HPE1 (236100). [from OMIM]