FOXN1 deficiency leads to thymic aplasia, alopecia, and nail dystrophy, accounting for the nude/severe combined immunodeficiency (nu/SCID) phenotype in humans and mice.
Alterations in the transcription factor FOXN1 gene, expressed in the mature thymic and skin epithelia, are responsible for human and murine athymia and prevent the development of the T-cell compartment associated to ectodermal abnormalities such as alopecia and nail dystrophy.
As in mice, also in humans this form is characterized by an intrinsic defect of the thymus, congenital alopecia and nail dystrophy and is due to mutations of the FOXN1 gene, as well.