pachyonychia congenita [Gk, pachy + onyx, nail; L, congenitus, born with] , a congenital deformity characterized by abnormal thickening and raising of the nails on the fingers and the toes and thickening of skin on the palms of the hands and the soles of the feet. The papillae of the tongue also atrophy, causing a whitish coating over the lingual surface.
