KID syndrome shares many features with IFAP although most people with KID syndrome have thick, hard skin on the palms of the hands and soles of the feet (palmoplantar keratoderma) and hyperkeratotic plaques with an erythematous base (erythrokeratoderma rather than ichthyosis). Here, MBTPS2 is linked to hereditary palmoplantar keratoderma.