Among these genes and their corresponding Mendelian disorders are CDSN (peeling skin syndrome 1), FLG (ichthyosis vulgaris), FLG2 (peeling skin syndrome 2), CASP14 (autosomal recessive congenital ichthyosis), KRT6A and KRT16 (pachyonychia congenita), CAST (peeling skin with leukonychia), NFKBIA (ectodermal dysplasia), TERT (dyskeratosis congenita), JUP (palmoplantar keratoderma), CSTA (peeling skin syndrome 4), and CTSB (keratolytic winter erythema). The gene discussed is CTSB; the disease is pachyonychia congenita.