Expanding the Nude SCID/CID Phenotype Associated with FOXN1 Homozygous, Compound Heterozygous, or Heterozygous Mutations

The study investigated the expanded phenotype associated with FOXN1 mutations in a cohort of 18 patients, including 11 homozygous, 2 compound heterozygous, and 5 heterozygous individuals, all with recurrent severe infections. It was found that while congenital athymia, alopecia, and nail dystrophy are hallmark features of the syndrome, they were not always present. Nearly 50% of the patients developed Omenn syndrome, and a SCID-like phenotype was observed in 4 heterozygous patients from the same family. The study suggested that the clinical severity is influenced by the residual activity of the gene product, and in the heterozygous family, a negative dominance mechanism or additional mutations might be involved.