Each column keeps its native condition scope. Initial features are displayed alphabetically, not ranked by clinical importance. Counts remain separate, and an empty cell does not mean a feature cannot occur.
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People with this form of SCID are missing functional immune cells called T cells, which normally recognize and attack foreign invaders to prevent infection. Without functional T cells, affected individuals develop repeated and persistent infections starting early in life. The infections result in slow growth and can be life-threatening; without effective treatment, most affected individuals live only into infancy or early childhood.","mondoId":"MONDO:0011132","records":[{"frequencyKind":"range","key":"136c28f293b8170f9f9a78f0166e43df4d28f50c77de1f901d40bd697d9084ba","raw":{"aspect":"P","body_system":"skin","disease_id":"ORPHA:169095","disease_name":"Severe combined immunodeficiency due to FOXN1 deficiency","evidence":"TAS","frequency_raw":"HP:0040281","hpo_id":"HP:0005597","is_excluded":false,"label":"Congenital alopecia totalis","onset_id":null,"reference":"ORPHA:169095","source_release":"2026-06-23"},"sourceGroups":["orphanet"]},{"frequencyKind":"range","key":"2cc0b290468e258e2d269b863d85bed0a795bb472e624cfed516a90017bd2333","raw":{"aspect":"P","body_system":"skin","disease_id":"ORPHA:169095","disease_name":"Severe combined immunodeficiency due to FOXN1 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DYSTROPHY","evidence":"TAS","frequency_raw":null,"hpo_id":"HP:0001596","is_excluded":false,"label":"Alopecia","onset_id":"HP:0003577","reference":"OMIM:601705","source_release":"2026-06-23"},"sourceGroups":["omim"]},{"frequencyKind":"range","key":"d87f4252cea29df8772642cafe921d13bd812768da150b61145ce038c7f6ebf8","raw":{"aspect":"P","body_system":"immune","disease_id":"ORPHA:169095","disease_name":"Severe combined immunodeficiency due to FOXN1 deficiency","evidence":"TAS","frequency_raw":"HP:0040281","hpo_id":"HP:0002721","is_excluded":false,"label":"Immunodeficiency","onset_id":null,"reference":"ORPHA:169095","source_release":"2026-06-23"},"sourceGroups":["orphanet"]},{"frequencyKind":"range","key":"f5c058a27d3a9ad5fc6c2ed6fcaf60c2373f2a75c93cff7a38f5942a4b29bcb1","raw":{"aspect":"P","body_system":"skin","disease_id":"ORPHA:169095","disease_name":"Severe combined immunodeficiency due to FOXN1 deficiency","evidence":"TAS","frequency_raw":"HP:0040281","hpo_id":"HP:0001807","is_excluded":false,"label":"Ridged nail","onset_id":null,"reference":"ORPHA:169095","source_release":"2026-06-23"},"sourceGroups":["orphanet"]}],"referenceLabels":{},"references":{"causeHtml":"","identityNote":"MONDO cross-references identify native condition entries. Ancestor membership does not transfer phenotype values between groups.","importantHtml":""},"sections":[{"bodyHtml":"T-cell immunodeficiency, congenital alopecia, and nail dystrophy results from mutations in the FOXN1 gene. This gene provides instructions for making a protein that is important for development of the skin, hair, nails, and immune system. Studies suggest that this protein helps guide the formation of hair follicles and the growth of fingernails and toenails. The FOXN1 protein also plays a critical role in the formation of the thymus, which is a gland located behind the breastbone where T cells mature and become functional. Researchers suspect that the FOXN1 protein is also involved in the development of the central nervous system, although its role is unclear.
Mutations in the FOXN1 gene prevent cells from making any functional FOXN1 protein. Without this protein, hair and nails cannot grow normally. A lack of FOXN1 protein also prevents the formation of the thymus. When this gland is not present, the immune system cannot produce mature, functional T cells to fight infections. As a result, people with T-cell immunodeficiency, congenital alopecia, and nail dystrophy develop recurrent serious infections starting early in life.
","key":"forms","title":"What causes T-cell immunodeficiency, congenital alopecia, and nail dystrophy?"},{"bodyHtml":"T-cell immunodeficiency, congenital alopecia, and nail dystrophy also affects growth of the hair and nails. Congenital alopecia refers to an absence of hair that is apparent from birth. Affected individuals have no scalp hair, eyebrows, or eyelashes. Nail dystrophy is a general term that describes malformed fingernails and toenails; in this condition, the nails are often ridged, pitted, or abnormally curved.
Researchers have described abnormalities of the brain and spinal cord (central nervous system) in at least two cases of this condition. However, it is not yet known whether central nervous system abnormalities are a common feature of T-cell immunodeficiency, congenital alopecia, and nail dystrophy.
Source: MedlinePlus Genetics
","key":"overview","title":"Condition overview"}],"sharedSources":[],"slug":"t-cell-immunodeficiency-congenital-alopecia-and-nail-dystrophy","sourceDocuments":[{"name":"T-cell immunodeficiency, congenital alopecia, and nail dystrophy","reviewed":"2014-08","sections":{"causes":{"fetchedAt":"2026-10-20T20:25:24.033309+00:00","label":"Causes","pageSha256":"c55c917ae3d0a440056310d9fd4e83e9c53f3ff562b3a8a76e5d90111346c41d","sourceUrl":"https://medlineplus.gov/genetics/condition/t-cell-immunodeficiency-congenital-alopecia-and-nail-dystrophy/#causes","status":"available"}},"source_release":"2026-10-01","url":"https://medlineplus.gov/genetics/condition/t-cell-immunodeficiency-congenital-alopecia-and-nail-dystrophy"}],"sourceNote":"MedlinePlus descriptions and Causes; original HPO annotations.","takeawayHtml":"Cause explanations are from MedlinePlus Genetics. Feature values below retain their original sources and patient groups.","title":"T-cell immunodeficiency, congenital alopecia, and nail dystrophy"},"schemaVersion":1}