We report the histopathological and ultrastructural tissue analysis of extraocular muscle (EOM) obtained from a patient with seronegative myasthenia gravis (MG) with treatment-resistant ophthalmoplegia for 3.5 years. The EOM demonstrated predominantly myopathic features and ultrastructural evidence of mitochondrial dysfunction, but the most striking features were increased endomysial collagen and adipocyte replacement of muscle fibers. By contrast, control EOM from a patient undergoing strabismus surgery for a sensory exotropia in a nonseeing eye and a similar duration of deviation, showed normal muscle histology. Although the histopathological and ultrastructural findings largely resemble those of limb muscle in MG, the abundant endomysial collagen may be nonspecific and secondary to poor force generation as a result of chronic ophthalmoplegia.
Neurology Research Group (RR, JMH), Department of Medicine, University of Cape Town, Cape Town, South Africa; Division of Ophthalmology (RMR), Department of Surgical Sciences, University of Stellenbosch, Belville, South Africa; Division of Anatomical Pathology (KP), Department of Pathology, University of Cape Town, Cape Town, South Africa; Division of Ophthalmology (ADNM), Department of Surgery, University of Cape Town, Cape Town, South Africa; and Division of Neurology (JMH), Department of Medicine, University of Cape Town, Cape Town, South Africa.
Address correspondence to Jeannine M. Heckmann, PhD, E8-74 Neurology, Groote Schuur Hospital, Observatory, 7925 Cape Town, South Africa; E-mail: Jeanine.firstname.lastname@example.org
R. Rautenbach was supported by a Discovery Fellowship, J. M. Heckmann received a South African Medical Research Grant.
The authors report no conflicts of interest.