Is it ADEM, POLG, or both?

Abstract

Objective: To describe a child with apparent brain biopsy-confirmed acute disseminated encephalomyelitis (ADEM) but genetic confirmation of compound heterozygosity for DNA mutations of the polymerase γ (POLG) gene. Design: Case report. Setting: Tertiary referral center. Patient: A 4-year-old boy presented with ataxia and encephalopathy. Results: Magnetic resonance imaging demonstrated multiple focal areas of T2 prolongation. The patient's family refused steroid treatment. His symptoms improved then progressed. Magnetic resonance imaging findings also progressed. A cerebrospinal fluid specimen revealed myelin basic protein and oligoclonal bands. A brain biopsy specimen demonstrated demyelination, suggesting progression of ADEM. However, polymerase chain reaction amplification and sequencing revealed 2 heterozygous mutations of the POLG gene, suggesting mitochondrial disease. The patient died 9 months after his initial presentation. Conclusions: This case raises interesting questions about whether ADEM triggered severe neurologic degeneration in a patient with mitochondrial disease, whether mitochondrial disease predisposed to a pathologic immune response, or whether mitochondrial disease can mimic an autoimmune disease. Mitochondrial disease-causing mutations may help explain the poor outcome in some cases of apparent autoimmune central nervous system disease. ©2010 American Medical Association.