Mitochondrial Disorders

Chronic progressive external ophthalmoplegia (CPEO) belongs to a group of diseases collectively termed mitochondrial myopathies (Fig 14-8), in which mitochondria are abnormally shaped and increased in number. Muscle biopsy specimens may reveal ragged red fibers. In addition to CPEO, the syndrome is associated with atypical RP and various systemic abnormalities. When associated with cardiomyopathy and cardiac conduction defects (heart block), the disorder is known as Kearns-Sayre syndrome; onset is usually before the age of 10 years. The severity of the pigmentary retinopathy is highly variable. Many patients retain good visual function and a normal ERG signal. Other mitochondrial myopathies with pigmentary retinopathy include MIDD (maternally inherited diabetes and deafness; Fig 14-9), MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke), and NARP (neurogenic muscle weakness, ataxia, and retinitis pigmentosa) syndromes.

Figure 14-8 Chronic progressive external ophthalmoplegia (CPEO) and mitochondrial associated retinopathy. A, Color fundus photograph shows diffuse retinal pigment epithelial mottling. B, Corresponding mottled hyper- and hypofluorescence in the arteriovenous-phase fluorescein angiography image. C, Color photograph shows bilateral ptotic eyelids and eyes in a misaligned exotropic position from poor extraocular muscle function consistent with CPEO caused by a mitochondrial mutation.

(Courtesy of David Sarraf, MD.)

Figure 14-9 Maternally inherited diabetes and deafness (MIDD). Color fundus photograph (A), late fluorescein angiography frame (B), and fundus autofluorescence image (C) show retinal pigment epithelial atrophy in a perifoveal distribution in a patient with MIDD caused by a mitochondrial mutation. These findings were all symmetrically present in the fellow eye.

(Courtesy of Herb Cantrill, MD.)

Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.