Micronychia is defined as nails that are smaller than normal. Congenital micronychia occurs in Iso-Kikuchi and Zimmermann-Laband syndrome.

Iso-Kikuchi syndrome is characterized by various nail dysplasias including micronychia. The micronychia can be a small, medially located nail or a centrally placed "rolled micronychia." Any nail can be involved, but the most common is the index finger. A Y-shaped distal bony phalanx is common. Additional findings may include syndactyly, ear anomalies, and brachymesophalangy.

Zimmermann-Laband syndrome is a rare disorder characterized by micronychia; gingival hypertrophy; bulbous, soft nose and thick, floppy ears; hyperextensibility of joints; and, in a small percentage of patients, hepatosplenomegaly, hypertrichosis, and intellectual disability.

Some patients with Turner syndrome can have apparent micronychia due to overlapping of the nail plate by a thickened perionychium.