Polysaccharide storage myopathy--case report and literature review

Abstract

Polysaccharide myopathy is a rare form of storage muscular disorder. The clinical picture of this particular form of myopathy is unspecific. We report a 62-year-old woman with late-onset progressive weakness and wasting, affecting proximal muscles of the four limbs and the girdles. No myalgia, dysphagia nor symptoms of cardiac failure were observed. Muscle biopsy revealed a vacuolar myopathy with accumulation of amylopectin-like polysaccharide. This material was strongly PAS-positive and diastase-resistant. At electron microscopy, the deposits were composed of non-membrane-bound filamentous and granular material surrounded by numerous mitochondria. No enzyme deficiency was found. Clinical presentation of our patient was similar to the 16 cases reported in the literature. She did not have myocardiopathy and her survival is much longer. Hypothetic mechanisms of polysaccharide accumulation are reviewed.