A severe combined immunodeficiency characterized by congenital alopecia, severe T-cell immunodeficiency, and ridging, pitting or curving of all nails that has material basis in homozygous mutation in the FOXN1 gene on chromosome 17q11-q12. The disease is MONDO_0011132 (T-cell immunodeficiency, congenital alopecia, and nail dystrophy). Also known as: FOXN1 deficiency, alopecia immunodeficiency, alymphoid cystic thymic dysgenesis, severe T-cell immunodeficiency-congenital alopecia-nail dystrophy syndrome, winged helix deficiency.