The stiff-person syndrome (SPS) is most often an adult-onset sporadic acquired disorder characterized by progressive muscle stiffness with superimposed painful muscle spasms accompanied by electromyographic evidence of continuous motor activity at rest. SPS has been associated with autoimmune disorders, diabetes mellitus, thyrotoxicosis, and hypopituitarism with adrenal insufficiency (George et al., 1984). Approximately 60% of patients with SPS have antibodies to glutamic acid decarboxylase (GAD2, or GAD65; 138275), the rate-limiting enzyme in the synthesis of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA), suggesting an immune-mediated pathogenesis (Folli et al., 1993). Approximately 10% of patients develop SPS as a paraneoplastic neurologic disorder associated with antibodies to amphiphysin (AMPH; 600418), an intracellular protein associated with neuronal synaptic vesicle endocytosis (Burns, 2005). See also congenital stiff-man syndrome, or hereditary hyperexplexia (149400), which is caused by mutations in subunits of the glycine receptor gene (GLRA1, 138491; GLRB, 138492). Meinck and Thompson (2002) provided a detailed review of stiff-person syndrome. They also discussed 2 possibly related conditions, progressive encephalomyelitis with rigidity (PERM), a more severe disorder with other neurologic features, and stiff-limb or stiff-leg syndrome, a focal disorder.

Autoimmune polyglandular syndrome type I is characterized by the presence of 2 of 3 major clinical symptoms: Addison disease, and/or hypoparathyroidism, and/or chronic mucocutaneous candidiasis (Neufeld et al., 1981). However, variable APS1 phenotypes have been observed, even among sibs. In addition, some patients may exhibit apparent isolated hypoparathyroidism, an early manifestation of APS1 with peak incidence at around age 5 years; over longterm follow-up, the development of additional features of APS1 may be observed (Cranston et al., 2022).

Spastic paraplegia-23 (SPG23) is an autosomal recessive neurologic disorder characterized by childhood-onset spastic paraplegia resulting in gait difficulties and associated with pigmentary abnormalities, including premature graying of the hair and vitiligo-like or hyperpigmented skin lesions. Some patients may also have a peripheral neuropathy (summary by Lee et al., 2017).

Familial progressive hyperpigmentation with or without hypopigmentation (FPHH) is characterized by diffuse hyperpigmentation of variable intensity sometimes associated with cafe-au-lait macules and larger hypopigmented ash-leaf macules. These features, which involve the face, neck, trunk, and limbs, are seen at birth or develop early in infancy (summary by Wang et al., 2009 and Amyere et al., 2011). Also see familial progressive hyperpigmentation (FPH1; 614233).

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).

Any autoimmune disease in which the cause of the disease is a mutation in the FOXD3 gene.

Generalized vitiligo is an autoimmune disease characterized by melanocyte loss, which results in patchy depigmentation of skin and hair, and is associated with an elevated risk of other autoimmune diseases. It is a genetically complex disorder involving multiple susceptibility genes and unknown environmental triggers. Patients with generalized vitiligo have elevated frequencies of other autoimmune diseases, suggesting that these diseases involve shared genetic components (summary by Jin et al., 2010). Genetic Heterogeneity of Vitiligo-Associated Multiple Autoimmune Disease Susceptibility Additional forms of vitiligo-associated multiple autoimmune disease susceptibility have been mapped to chromosomes 1p31 (VAMAS2, 607836, associated with mutation in the FOXD3 gene, 611539), 7 (VAMAS3; 608391), 8 (VAMAS4; 608392), 4 (VAMAS5; 609400), and 6p21.3 (VAMAS6; 193200).

A rare deafness characterized by the association of bilateral sensorineural hearing loss and white hair with scattered black tufts, as well as skin areas of hyper- and hypopigmentation. Additional reported features include global developmental delay and moderate intellectual disability, growth retardation, microcephaly, hypotonia, mild dysmorphic facial features (deeply set eyes, broad nasal bridge, slight bowing of the upper lip), retinal depigmentation, anomalies of the fingers and toes, and white matter abnormalities on brain imaging.

Deafness-vitiligo-achalasia syndrome is characterized by the association of deafness, short stature, vitiligo, muscle wasting, and achalasia.

Familial cold autoinflammatory syndrome-3 is an autosomal dominant immune disorder characterized by the development of cutaneous urticaria, erythema, and pruritus in response to cold exposure. Affected individuals have variable additional immunologic defects, including antibody deficiency, decreased numbers of B cells, defective B cells, increased susceptibility to infection, and increased risk of autoimmune disorders (summary by Ombrello et al., 2012). For a discussion of genetic heterogeneity of FCAS, see FCAS1 (120100).

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).

Immunodeficiency-7 (IMD7) is an autosomal recessive immunologic disorder characterized by onset of recurrent bacterial and viral infections in infancy or early childhood. Affected individuals may also have features of immune dysregulation, including lymphadenopathy and presence of autoantibodies. Laboratory studies show increased serum IgE, low numbers of T cells, low TCR-alpha/beta cells, and increased TCR-gamma/delta cells. The disorder often results in death in childhood, although bone marrow transplant is effective (summary by Morgan et al., 2011 and Rawat et al., 2021).

Immunodeficiency-99 with hypogammaglobulinemia and autoimmune cytopenias (IMD99) is an autosomal recessive immunologic disorder characterized by the onset of recurrent sinopulmonary infections in early childhood. Laboratory studies reveal hypogammaglobulinemia with decreased memory B cells that show impaired class-switch recombination (CSR) and decreased somatic hypermutation (SHM). Due to abnormal antibody production and impaired self-tolerance, patients may develop autoimmune cytopenias, such as thrombocytopenia, or autoimmune features, such as vitiligo. There are also defects in the T-cell compartment (Kuhny et al., 2020).