MELAS masquerading as a systemic vasculitis.

Mitochondrial encephalomyopathy, lactic acidosis, and stroke (MELAS) is a mitochondrial genetic disorder caused by a point mutation, resulting in the substitution of guanine for adenine at nucleotide 3243 (A3243G). It is a multisystem disorder with variable manifestations and typically presents between the first and third decades of life. It should be suspected if a patient exhibits stroke-like episodes before age 40, encephalopathy characterized by seizures, dementia, or both, and lactic acidosis, ragged-red fibers in muscle, or both. We present the case of a 26-year-old white man suspected with primary central nervous system vasculitis admitted to our facility with profound constipation from severe intestinal dysmotility. Although his gastrointestinal and neurologic symptoms did not meet criteria for a specific vasculitic syndrome, his symptoms and blood test abnormalities were concerning for such a process. MELAS was included in our differential diagnosis because his symptoms failed to fit a defined vasculitic process. When genetic testing documented the presence of the point mutation A3243G, his diagnosis was changed. This case illustrates the importance of considering a mitochondrial genetic disorder in the differential diagnosis of patients who present to Rheumatologists with suspected unusual or atypical vasculitic symptoms.