ECHS1 catalyzes the second step of short chain fatty acid oxidation (FAO). FAO and isoleucine intermediates are reportedly normal. However, elevated valine intermediates, methacrylyl CoA and acryloyl CoA, are thought to damage the pyruvate dehydrogenase complex and the electron transport chain. Only a few cases are reported. All suffer global encephalopathy, severe developmental delay, and most die in infancy or early childhood. There is no effective treatment.

Triheptanoin is a medium chain (C7 oil) triglyceride, metabolized to heptanoic acid and C4/ C5 ketone bodies. C7 oil is an anaplerotic agent that replenishes TCA cycle intermediates by forming acetyl-CoA and propionyl CoA, subsequently metabolized to oxaloacetate.  Acetyl-CoA and oxaloacetate condense to form citric acid.

The patient presented at age 6 months with Leigh syndrome, global developmental delay, ptosis, oscillatory eye movements, mixed tone abnormalities, hyperreflexia and bilateral Babinski signs. The brain MRI scan demonstrated signal abnormalities in subcortical nuclei. At age 46 months, triheptanoin was administered enterally as an ascending dose (5% to 35% of total daily calories), using an approved individual patient IND. Safety measures (blood and urine chemistries, EKG), neurological and physical examinations and motor function assessments (CHOP-INTEND and GMFM-88) were performed quarterly.

The patient has been stable clinically with subtle improvements in awareness, posture, purposeful movements, mood and sleep pattern during 12 months of treatment. CHOP-INTEND improved 8 points  (baseline 34/64; 12 month 42/64); and the GMFM-88 improved 14 points (baseline 9/264; 12 month 23/ 264). CNS score improved 8 points (baseline 42/76; 12 month 50/76).  The drug has been well tolerated with no evidence of regression or serious side effects.

Triheptanoin may be useful in the treatment of ECHS1D.