Congenital onychodysplasia of the index fingers. Iso and Kikuchi syndrome.

Congenital onychodysplasia of the index fingers (Iso and Kikuchi syndrome) is characterized by five criteria: (1) congenital occurrence, (2) unilateral or bilateral index finger involvement, (3) variability in nail appearance, (4) possible hereditary involvement, and (5) frequently associated bone anomalies. Emphasis is placed on the configuration of the lunula, which is deformed and plays an important role in shaping the free edge of the nail plate. To our knowledge, this deformity has not been previously described in this syndrome.