Noninvasive evaluation of adult onset myopathy from carnitine palmitoyl transferase II deficiency using proton magnetic resonance spectroscopy

Objective. The adult onset metabolic myopathy of carnitine palmitoyl transf erase II (CPT II) deficiency is under-recognized, in part due to variable d egrees of enzyme deficiency and symptomatology, as well as limitations in m eans for noninvasive evaluation. We describe a proton magnetic resonance sp ectroscopy (MRS) technique, using a standard clinical magnetic resonance im aging scanner, to diagnose and help monitor the response to therapy in adul t CPT II deficiency. Methods. A 53-year-old woman presented with a long standing history of diff use aching and fatigue provoked by high fat intake, fasting, or prolonged e xertion. Muscle biopsy revealed myopathic features and a deficiency (33% of control) of CPT II activity with elevated palmitoyl carnitine. Proton MRS of the soleus muscle was performed using a 1.5 Tesla scanner before and dur ing dietary therapy. Results, Proton MRS revealed shortening of the transverse relaxation time ( T-2), consistent with increased acetylation of the carnitine pool. The symp toms resolved completely by treatment with frequent feedings of a high carb ohydrate diet low in long chain fatty acids supplemented with medium chain triglycerides and L-carnitine. Recovery of normal muscle MRS and carnitine T-2 relaxation was documented by the third month of therapy. Conclusion. Proton MRS is a novel, potentially useful, and readily availabl e adjunct in the diagnosis and therapeutic monitoring of muscle CPT II defi ciency.