Successful treatment of a progressive myopathy using a modified ketogenic diet with medium-chain triglycerides

A spectrum of disorders of fat metabolism has now been identified with pathologic conditions of muscle. The reversal of some of these disorders by treatment has led to their clinical importance. A 10-year-old-boy had a history of progressive weakness. Examination revealed hepatomegaly, marked lumbar lordosis, oral ptosis, facial displegia, decreased phonation, difficulty in swallowing, depressed reflexes, and generalized weakness: the boy was unable to rise from the floor. His muscle and liver enzymes were mildly elevated. A muscle biopsy showed small type I fibers with vacuoles containing oil red O-staining material. Muscle carnitine was 0.84 μm/gm wet weight. (S. DiMauro). Incubation of muscle homogenate with palmitate, with or without carnitine, showed deficient utilization. The child was placed on a modified ketogenic diet using medium-chain triglycerides. He markedly improved over the next 7 months as evidenced by: increased pulmonary function (FVC 32 to 76 percent); improved ambulation (100 yd/217 seconds was now 100 yd/37 seconds); repeated muscle biopsy demonstrated no fiber atrophy, type II predominance, only a few type I fibers, and increased oil red O-staining material. Discontinuation of the diet therapy on two different occasions caused a worsening of muscle strength. Whether this child's dramatic clinical improvement is due to the direct metabolism of the medium-chain fatty acids or of their metabolites is unclear at this time.