A Caribbean case of phosphoglycerate mutase deficiency: Relevance of forearm exercise test and electroneuromyography with long exercise test in the diagnosis strategy of rare muscle glycogenosis

Muscle phosphoglycerate mutase deficiency is a very rare muscle metabolism disorder which inheritance pattern is autosomal recessive. Exercise-induced muscle cramps and myoglobinuria are main clinical features. The skeletal muscle biopsy often shows tubular aggregates. We report a new patient with muscle phosphoglycerate mutase deficiency revealed by rhabdomyolysis episodes. Forearm exercise test revealed blunted lactate increase associated with hyperammonemia and ENMG with long Exercise Test disclosed a post-exercise decrease in CMAP amplitude, demonstrating the important contribution of both tests combined for the diagnosis of rare muscle glycogenosis.