Congenital agenesis of the superficial posterior compartment calf muscles in a 13-month-old infant.

Muscle agenesis may induce cosmetic and functional deficits, particularly if the muscle is an axial limb or a large muscle. Limb muscle agenesis is a rare condition. Here, the authors report the case of a 13-mo-old girl with unilateral atrophic calf and gait abnormality. Magnetic resonance imaging confirmed agenesis of the posterior superficial compartment of the calf. The patient showed an out-toeing calcaneal gait and fibular length discrepancy secondarily during growth. Normal embryology and the differential diagnostic point of foot deformity as well as the clinical implications of calf agenesis are described.