Patients will be excluded if they cannot travel to the NIH or CNMC because of their medical condition. The PI may decline to enroll a patient for other reasons. Other criteria that may lead to exclusion include, for example, residing in a hospital, sub-optimal metabolic control as determined by Dr. Venditti s review of the laboratory data, any patient who requires dialysis once or more/week and weighs <40 kg, any patient who is being treated for an intercurrent infection with antibiotics or has evidence of an acute infection and has metabolic symptoms, any patient who does not have a regular/local metabolic, genetic or endocrine physician and/or a family physician, pediatrician, or internist, and any patient who may be metabolically unstable but not acutely ill. Each family may be contacted by Dr. Venditti or a staff member working with him one week prior to a pending inpatient admission to confirm that the patient is metabolically stable and ready to visit the NIH in a state of relative health, with an adequate supply of special formulas, medications, supplements, and if needed, medical equipment such as feeding pumps and replacement parts for feeding tubes.