Complex polysaccharide inclusions in the skeletal muscle of stranded cetaceans.

Skeletal muscle samples were examined post-mortem in 148 cetaceans over a 12-year period. Histological analysis included haematoxylin and eosin (HE) and periodic acid-Schiff (PAS) staining with and without diastase digestion. In addition, histological muscle sections were immunostained for ubiquitin and fast and slow heavy-chain myosin isoforms. PAS-positive, diastase-resistant inclusions were detected in 26 animals from 11 different species. Older cetaceans were preferentially affected. These intrafibre inclusions varied from large aggregates to multiple coarse granules and were typically associated with type II fibres. All diastase-resistant inclusions were positive for ubiquitin. These features resembled those inclusions described as complex polysaccharide in horses. Based on these histological findings and the ubiquitin staining pattern, a morphological diagnosis of complex polysaccharide storage myopathy is proposed.