[MIM*148600 & MIM*244850] the occurrence of symmetric diffuse or patchy areas of hypertrophy of the horny layer of the epidermis on the palms and soles; a group of ectodermal dysplasias of considerable variety, and either autosomal dominant or recessive inheritance. SYN: ichthyosis palmaris et plantaris, keratoderma palmare et plantare, keratoderma symmetrica, keratoma plantare sulcatum, keratosis palmaris et plantaris, tylosis palmaris et plantaris.