We report on the autopsy study of a premature boy with multiple joint contractures who died soon after birth of severe lung hypoplasia. Muscle histology showed PAS-positive vacuoles, and electronmicroscopy revealed massive subsarcolemmal and intermyofibrillar accumulation of glycogen. Biochemical analysis of fresh-frozen muscle tissue disclosed increased glycogen content and a complete lack of phosphofructokinase (PFK) activity. The brain showed focal cerebral and diffuse cerebellar white matter gliosis, and patchy loss of internal granular and Purkinje cells in the cerebellar cortex. The spinal cord was normal. This report describes the first case of PFK deficiency, presenting as a lethal fetal akinesia sequence.