Mitochondrial pseudomyasthenia

Selected case from the Arkadi M. Rywlin International Pathology Slide Series: Mitochondrial myopathy presenting with chronic progressive external ophthalmoplegia (CPEO): a case report

A 43-year-old female patient diagnosed with chronic progressive external ophthalmoplegia (CPEO) because of mitochondrial myopathy documented by muscle biopsy is presented. The chief complaints were represented by blepharoptosis and ophthalmoplegia. The muscle biopsy was evaluated by histology, using the appropriate histochemical and histoenzimological stains. Ragged red fibers with Gomori trichrome stain were seen, which showed cytochrome c oxydase deficiency and abnormal succinate dehydrogenase staining in around 20% of muscle fibres. Electron microscopy was also performed which demonstrated abnormal, hyperplastic, pleomorphic, and hypertrophic mitochondria, characterized by paracrystalline inclusions arranged in parallel rows ("parking-lot" inclusions), consisting of rectangular arrays of mitochondrial membranes in a linear or grid-like pattern. In conclusion, mitochondrial myopathy was definitely diagnosed. Although molecular analysis, which was subsequently carried out, failed to reveal mutations in the mitochondrial DNA or in selected nuclear genes, the pathologic diagnosis was not changed. The differential diagnosis of CPEO with other forms of ocular myopathies as well as the possible association of CPEO with systemic syndromes is discussed. Ophtalmologists and medical internists should always suspect CPEO when dealing with patients affected by ocular myopathy, either in its pure form or in association with other myopathic or systemic signs.

Curtains

A 55-year-old immunocompetent man presented with headache, nausea, progressive bilateral upper lid ptosis, and diplopia. Examination showed bilateral asymmetric upper lid ptosis with limited adduction and elevation of both eyes. Cranial magnetic resonance imaging revealed enhancing intra-axial and extra-axial midbrain lesions. Blood and cerebrospinal fluid were positive for cryptococcal antigen and cerebrospinal fluid fungal cultures grew Cryptococcus neoformans. Treatment with liposomal amphotericin B and flucytosine resulted in complete resolution of his neurological deficits and lesions on neuroimaging. Patients with cryptococcal meningitis may rarely present with bilateral cranial nerve III dysfunction.