Inherited metabolic myopathy with storage of glycoproteins and glycosaminoglycans

Two related patients (mother and daughter, ages 28 and 5 years) showed mild to moderate weakness and atrophy of facial and shoulder muscles with congenital onset and minimal progression. Serum creatine kinase was elevated in the child. Muscle biopsy showed normal light-microscopic and histochemical findings, but scattered sarcoplasmic vacuoles with storage of granular material were evident on electron microscopy. Storage of granular material was also identified in fibroblasts which were weakly PAS-positive, stained metachromatically with toluidine blue and orthochromatically with alcian blue. Muscle glycogen values were low-normal. Repeated biochemical studies of cultured fibroblasts identified excessive storage of glycosaminoglycans and glycoproteins. The uptake of 3H-glucosamine in cultured fibroblasts was 1.7-3.4 times greater in the patients than in control individuals, while the rate of turnover of the radioisotope was normal. These findings suggest that the genetic defect in this inherited metabolic myopathy is related to excessive synthesis of glycosaminoglycans and glycoproteins.