In a woman with a slowly progressive adult onset proximal myopathy, mus- cle biopsy showed storage of zyxwv PAS positive material in type 1 fibers. This material consisted of a branched chain polysaccharide associated with a mucoprotein. No abnormality of glygogen-pathwayenzymes was detected. This suggested that this polysccharide accumulation occurred because the polysaccharide was laid down in a non-bioavailable form. The clinical and histochemical features in this patient and in the few similar reported cases indicate that polysaccharide storage myopathy is a distinct entity that is al- lied to the glycogen storage myopathies. MUSCLE & NERVE 11~349-355 1988 POLYSACCHARIDE STORAGE MYOPATHY A.J. THOMPSON, MD, MRCPI, M. SWASH, MD, FRCP, MRCPath, E.L. COX, FIMLS, D.A. INGRAM, MB, A. GRAY, BSc, and M.S. SCHWARTZ, MD zyxwvut Disorders of glycogen metabolism are uncom- mon causes of adult onset my~pathies.~ zyxwvu A number of cases have been r e p ~ r t e d ~ ” ~ ~ ’ ~ - ’ ~ ~ ’ ~ , ~ ~ in ’ which muscular weakness was associated with deposition of an amylopectin-like substance in the muscle fi- bers with no abnormality of glycolytic enzymes to suggest a relationship to the glycogenoses. These patients have shown marked clinical heterogene- ity. In two cases’” ’ similar insoluble polysaccha- ride storage was associated with muscle phosphof- ructokinase deficiency. In this report we describe a patient with polysaccharide storage myopathy and suggest that this represents a hitherto uncha- racterized storage disorder of muscle. CASE REPORT A 46-year-old woman presented with a 16-year history of slowly progressive proximal weakness, beginning in the right leg and then involving both legs. For the past 5 years she had also noticed proximal weakness in her right arm. She walked with a pronounced waddling gait and had diffi- culty walking on her heels because of shortening ~ ~ ~~~ From the Departments of Neurology (Drs. Thompson, Swash, ingram, and Schwartz) and Pathology (Drs. Swash, Cox, and Gray), The London Hospital, London, UK. Acknowledgment: We thank Mr. G. Whitfield of the Institute of Child Health, London, WC1 for the enzyme determinations Address reprint requests to Or Swash at the The London Hospital, Lon- don El IBB, UK. Accepted for publication February 23, 1987 01 48-639)(/1104/0349 $04.0017 zyxwvutsrqp 0 1988 John Wiley & Sons, Inc. of the Achilles tendons. There was symmetrical weakness of trunk and hip muscles and of knee extension. Distal leg muscles were of normal strength. There was moderate proximal weakness of the right arm, and the left arm was less af- fected. There was no facial or external ocular muscle weakness. Sensory examination was nor- mal. The knee jerks were absent. Routine hematological and biochemical investi- gations were normal. The blood creatine kinase was 180 IU/L (normal < 160 IU/L). The ECG was normal. Concentric needle EMG studies showed short duration, low amplitude, polyphasic motor unit potentials in the deltoid, quadriceps, and ti- bialis anterior muscles. Complex repetitive dis- charges were recorded in the deltoid muscle. The interference pattern was full on slight exertion. Single-fibre EMG recordings in the extensor digi- torum communis muscle revealed normal fibre density, but in several units late components were recorded, and these usually showed increased jit- ter (60-100 ks; normal < 55 us).“ Motor and sensory nerve conduction velocities were normal. CT scanning of the legs showed reduced attenua- tion, suggestive of fat replacement in the lateral compartment of quadriceps and flexor compart- ments of the thigh. The rectus femoris, sartorius, adductor magnus, and gracilis muscles showed normal attenuation (Fig. 1). An open biopsy was taken from the left biceps and a needle biopsy was taken from the left quadriceps (vastus lateralis). Muscle Pathology. In the biceps muscle striking abnormalities were seen (Fig. 2). Light microscopy Polysaccharide Storage Myopathy MUSCLE zyxw 8, NERVE April 1988 349