Congenital anomalies of the nail unit

The characteristic morphology of the nail unit is determined at the moment of conception by the chromosomal content of the zygote. Subsequent mitotic events including deletion, duplication, breakage, etc. also may contribute to nail deformity. In utero conditions are another factor that may affect the appearance of the nail unit. This article identifies conditions of the nail unit that are congenital in nature and deserve special attention to treatment plans that may or may not be beneficial.