Background: Fatty acid oxidation disorders (FAODs) include more than 15 distinct disorders with variable clinical manifestations. After the introduction of newborn screening using tandem mass spectrometry, early identification of FAODs became feasible. This study describes the clinical, biochemical and molecular characteristics of FAODs patients detected by newborn screening (NBS) compared with those of 9 patients with symptomatic presentations.

Methods: Clinical and genetic features of FAODs patients diagnosed by NBS and by symptomatic presentations were reviewed.

Results: Fourteen patients were diagnosed with FAODs by NBS at the age of 54.8 ± 4.8 days: 5 with very-long-chain acyl-CoA dehydrogenase (VLCAD) deficiency, 5 with medium chain acyl-CoA dehydrogenase (MCAD) deficiency, 1 with primary carnitine deficiency, 1 with carnitine palmitoyltransferase 1A (CPT1A) deficiency, 1 with long-chain 3-hydroxyacyl-CoA dehydrogenase or mitochondrial trifunctional protein (LCAHD/MTP) deficiency, and 1 with short chain acyl-CoA dehydrogenase (SCAD) deficiency. Three patients with VLCAD or LCHAD/MTP deficiency developed recurrent rhabdomyolysis or cardiomyopathy, and one patient died of cardiomyopathy. The other 10 patients remained neurodevelopmentally normal and asymptomatic during the follow-up. In 8 patients with symptomatic presentation, FAODs manifested as LCHAD/MTP deficiencies by recurrent rhabdomyolysis or cadiomyopathy (6 patients), and VLCAD deficiency by cardiomyopathy (1 patient), and CPT1A deficiency by hepatic failure (1 patient). Two patients with LCHAD/MTP deficiencies died due to severe cardiomyopathy in the neonatal period, and developmental disability was noted in CPT1A deficiency (1 patient).

Conclusions: NBS helped to identify the broad spectrum of FAODs and introduce early intervention to improve the clinical outcome of each patient. However, severe clinical manifestations developed in some patients, indicating that careful, life-long observation is warranted in all FAODs patients.