HISTOCHEMICAL AND ULTRASTRUCTURAL ANALYSIS OF THE MITOCHONDRIAL CHANGES IN A FAMILIAL MITOCHONDRIAL MYOPATHY

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Abstract
Two familial cases of progressive external ophthalmoplegia with involvement of pharyngeal and distal muscles are presented. Ragged-red fibers were found in both cases. Excessive amounts of RNA, as evidenced by the acridine orange-induced fluorescence, were noted in amny muscle fibers, mostly in the ragged-red fibers. Ultrastructurally, numerous mitochondrial changes with paracrystalline formations were noted. Those formations were observed in 3 forms, and a 3 dimensional reconstruction is proposed which suggests that the paracrystalline formations consist of undulating parallel leaflets joined along the top of the undulations. Small transverse bridges between neighboring cristae and between cristae and paracrystalline formations are emphasized. Those mitochondrial abnormalities are thought to represent the morphological expression of a biochemical deficiency in the inner membrane. The biochemical defect may to a multiplication of the mitochondria with increase in their volume and proliferation of the cristae to improve energy production. Bridges between the modified inner membranes may induce attachment of the neighboring cristae and result in paracrystalline formations.