Peculiar facial appearance and generalized brachydactyly in a patient with congenital onychodysplasia of the index fingers (Iso-Kikuchi syndrome).

We report on a patient with clinical manifestations consistent with a diagnosis of congenital onychodysplasia of the index fingers (COIF). This syndrome has been found mainly in Japan, and as far as we know, this is the first case reported in Italy. In addition to the typical bilateral split nail of the second finger, the patient showed bilateral inguinal hernia, a peculiar face, and short hands. The metacarpophalangeal profile showed a generalized brachydactyly with all the hand long bones below x3 SD. The patient's father showed a peculiar kind of micronychia on both the fifth toes, suggesting a possible autosomal dominant transmission of the syndrome. In utero ischemia of the palmar digital artery and a dysplastic change in the crescent-shaped cap of the distal phalanx are the two main candidate pathogenetic mechanisms that have been proposed. In our opinion, the gradual broadening of the spectrum of this syndrome brings support to the hypothesis of a basal dysplastic pathogenetic mechanism involving not only the index fingers but also perhaps other tissues outside. We think that for the moment the definition of COIF for this syndrome should be maintained, the alternative proposed term "congenital onychodysplasia" being too indefinite.