Mitochondrial Encephalopathy with Lactic Acidosis and Stroke (MELAS) presenting as an apparent neoplastic process (P5.015)

OBJECTIVE: To report a unique case of a stroke-like episode in MELAS presenting as a possible neoplastic process. BACKGROUND: MELAS is well known to present with acute onset of stroke-like symptoms, a mitochondrial pattern of inheritance and lactic acidosis. Its phenotype is more heterogeneous however, and unusual presentations of this disorder may be mistaken for more common conditions. DESIGN/METHODS: A 50 year old Caucasian female presented with the gradual onset of worsening headaches, difficulty reading, nausea, vomiting, shortness of breath and upper abdominal pain. Of note, she had a history of progressive hearing loss which began twenty years prior, a right MCA stroke, idiopathic gastroparesis, CKD, and depression. An MRI demonstrated a diffuse hyperinstensity of her right and left temporal lobes which was thought to represent either viral encephalitis or multifocal low grade glioma. An evolving infarct was considered improbable. RESULTS: A biopsy of the anterior middle temporal gyrus from the cortical surface to deep CSF spaces demonstrated a mild increase in cellularity secondary to increased astrocytes and microglia. There were no granulomas, microglial nodules, or neuronophagia. There was no evidence of vasculitis. Histological staining highlighted numerous reactive astrocytes accentuated in the cortex and present in the white matter and increased microglia in the cortex and white matter. There was no significant T- or B-cell inflammation. An LP with cytology was negative for malignancy. A mitochondrial DNA study was positive for a heteroplasmic m.3243A>G in the MTTL1 (tRNAleu) gene, the most common mutation in MELAS syndrome. CONCLUSION: MELAS can mimic more common disorders. The slow onset of her symptoms and the MRI9s appearance led to suspicion for neoplasm. This is the first report to our knowledge where MELAS has presented as such. Documentation of this and other unusual presentations of mitochondrial disease is crucial to appropriate diagnosis of the condition. Disclosure: Dr. Rothstein has nothing to disclose. Dr. Haq has nothing to disclose.