Ocular myopathies.

Ocular myopathies are manifested by primary and progressive involvement of extraocular muscles. In most cases of involvement of extra-ocular muscles a biopsy from somatic muscles studied by histochemistry and electron microscopy permits to make the diagnosis of the underlying condition. The two main clinico-pathological types of ocular myopathies are the oculocraniosomatic syndrome (Kearns-Sayre syndrome) and oculopharyngeal muscular dystrophy. The oculocraniosomatic syndrome is a multisystemic disorder and its histopathological hallmark is the presence of ragged-red muscle fibres which contain aggregates of abnormal mitochondria, often with paracrystalline inclusions. In the oculopharyngeal muscular dystrophy are observed muscle fibres with rimmed vacuoles and intranuclear tubular filamentous inclusions about 8.5 nm in external diameter. The rimmed vacuoles may occur in other muscle diseases but the intranuclear inclusions appear to be specific for oculopharyngeal muscular dystrophy. Their nature is unknown.