Mitochondrial trifunctional protein deficiency: A severe fatty acid oxidation disorder with cardiac and neurologic involvement

Objective To determine the spectrum of presentation, including both clinical and biochemical abnormalities, and the clinical course in a cohort of patients with complete mitochondrial trifunctional protein (MTP) deficiency, a rare inborn error of mitochondrial fatty acid oxidation. Study design A questionnaire was sent to the referring physicians from 25 unselected MTP-deficient patients. Results Twenty-one patients could be included. Questionnaires about four patients were not returned. Nine (43%) patients presented with rapidly progressive clinical deterioration; six (67%) of them had hypoketotic hypoglycemia. The remaining 12 patients presented with a much more insidious disease with nonspecific chronic symptoms, including hypotonia (100%), cardiomyopathy (73%), failure to thrive, or peripheral neuropathy. Ten patients (48%) presented in the neonatal period. Mortality was high (76%), mostly attributable to cardiac involvement. Two patients who were diagnosed prenatally died despite treatment. Conclusion Complete MTP deficiency often presents with nonspecific symptomatology, which makes clinical recognition difficult. Hypotonia and cardiomyopathy are common presenting features, and the differential diagnosis of an infant with these signs should include MTP deficiency. In spite of early diagnosis and treatment, only a few patients with this condition have survived.