A 14-year-old boy presents with a subacute, painless loss of central vision in his right eye, which began 2 months ago, followed by similar symptoms in his left eye a month later. Fundoscopy reveals disc hyperemia and a characteristic peripapillary telangiectatic microangiopathy. A family history is notable for a maternal uncle who experienced similar vision loss in young adulthood. What is the most likely underlying diagnosis?