Fatal familial infantile glycogen storage disease: multisystem phosphofructokinase deficiency.

An infant girl of consanguinous Bedouin parents suffered from fatal early onset of progressive generalized muscle weakness. Her older brother suffered from similar weakness and cardiomyopathy, which led to his death at the age of 21 months. A muscle biopsy performed on the propositus at the age of 9 months was PAS-negative, and showed nonspecific myopathic changes. A second muscle biopsy, performed at 21 months of age, a few days before her death, and postmortem study of heart and liver, disclosed excessive extralysosomal glycogen storage and reduced phosphofructokinase-1 (PFK-1) activity. Because the genes encoded for PFK-1 in liver and muscle are located on separate chromosomes, the reduced enzyme activity in both tissues could not be related to a single mutation for this enzyme. Activity of 6-phosphofructose-2-kinase (PFK-2), a recently discovered physiological activator to all PFK-1 isozymes, was normal in the liver. The possibility that this multisystem PFK-1 deficiency may be related to the absence of a yet unknown activator, common to all PFK-1 isozymes, is discussed.