Treatment of 3-MCC deficiency involves reducing dietary leucine intake using a special leucine-depleted formula or instituting a general protein restricted diet. With onset of illness, IV glucose is needed and the acidosis must be corrected. Both carnitine and glycine supplementation have proven beneficial. Patients should undergo an early trial of biotin supplementation on the possibility that the defect is with biotin metabolism rather than isolated 3-MCC; biotin may be discontinued if there is no response.
Because the diagnosis and therapy of 3-MCC deficiency is complex, the pediatrician is advised to manage the patient in close collaboration with a consulting pediatric metabolic disease specialist. It is recommended that parents travel with a letter of treatment guidelines from the patient’s physician.