Hypoplasia of the thumb refers to a spectrum of clinical abnormalities ranging from a slightly small digit to complete absence (or aplasia) of the thumb unit. As a component of radial dysplasia, thumb hypoplasia can be either an isolated entity or seen in conjunction with other elements of radial longitudinal deficiency. Treatment of this condition initially involves identifying and addressing co-morbid anomalies in other body systems. The severity of thumb hypoplasia is then graded so that appropriate treatment methods can be instituted. The goal of treatment is ultimately to provide the child with a stable and functional thumb unit.