Mitochondrial myopathy presenting as rhabdomyolysis.

A 37-year-old white woman presented with acute bilateral hamstring pain after hiking. She had a creatine kinase level of 11,144 U/L. Rhabdomyolysis was diagnosed and the patient was admitted for intravenous fluid hydration. The patient continued to have exercise-induced myalgias and elevations in her creatine kinase level. Rheumatologic causes were ruled out and results from electromyogram testing were nondiagnostic. A muscle biopsy revealed a mitochondrial myopathy. The 22 mitochondrial DNA and transfer RNA genes were sequenced. An A-to-G transition was found at nucleotide position 4281 in the transfer RNA isoleucine gene. The patient was placed on a regimen of riboflavin, vitamin C, and coenzyme Q10, which provided mild relief. The patient returned to the emergency department 2 more times after vigorous exercise, with creatine kinase levels as high as 2800 U/L. At last follow-up, the patient was using a fentanyl citrate transdermal patch, which enabled her to perform moderate exercise without pain.