Discussion of polysaccharide storage myopathy (PSSM) on four cases

Polysaccharide storage myopathy (PSSM) is characterized by abnormal polysac charides and increased glycogen storage in the musculature of affected hors es, which are predisposed for recurrent exercise-induced myopathies. A fami lial predisposition for PSSM has been reported in American Quarter Horses ( AQH) and related breeds. Two AQH and a Swiss Warmblood were presented to us for recurrent rhabdomyolysis and one Haflinger for severe exercise intoler ance. The signalment, clinical examination, and serumactivity valves of CK, ASAT and LDH before and after an exercise test lead to the tentive diagnos is of PSSM, which was confirmed by the histopathological evaluation of musc le biopsies. Increased muscle glycogen and pathognomonic, PAS-positive amyl ase-resistent polysaccharides were present in all the cases. Our report ill ustrates that PSSM must be included in the differential diagnosis of exerci se induced recurrent myopathies in AQH as well as in horses of other breeds in Europe.