Ultrastructure of the cyst wall of S Lindemanni with pathological correlations

ABSTRACT

Electron microscopy of skeletal muscle biopsy from a case of human sarcocystosis revealed a new cyst type of S. lindemanni. The sarcocyst appeared large having a thick cyst wall with evident septa extending into the cyst and, characteristically, broad branched cauliflower like protrusions extending into the pericystic zone. This cyst type appeared to be highly pathogenic. In addition to the complete myofibrillar lysis of the infected muscle fibre there were delamination of the neighbouring myofibres, disruption of the sarcomeric orientation with diarrangement and bending of the Z bands and loss of the T and L-myofibrillar pattern in the pericystic zone. Features of myositis such as the presence of abundant lysosomal structures, myofibrillar disarray and glycogen formations were detected. These cytopathogenic signs were obviously attributed to the structural criterion of the cyst wall. The findings not only invalidate the concept that pathological conditions associated with human sarcocytosis are accidental, but also stress the value of electron microscopy in inducing relevant typing of sarcocysts on basis of their morphologically expressed pathogenic properties