Short or absent digits may have several possible causes. A thumb may be hypoplastic in that it is smaller than the opposite side thumb and has deficient muscles and ligament instability. In an extreme situation, a thumb may be totally absent. An absent thumb may occur in isolation as a congenital hand anomaly, or it may occur in association with radial dysplasia (formerly called radial clap hand). Radial dysplasia with absent thumb may be part of the VATER association of anomalies to include vertebral, anorectal atresia, tracheoesophageal fistula, and renal abnormalities.
