An asymptomatic infant with isolated 3-methylcrotonyl-coenzyme: a carboxylase deficiency detected by newborn screening for maple syrup urine disease.

UNLABELLED: We describe an asymptomatic male infant with isolated 3-methylcrotonyl-coenzyme A carboxylase deficiency who came to medical attention by newborn mass screening due to elevated blood leucine. The diagnosis was made by abnormal urinary organic acids at 20 days of age and was confirmed by assay of the carboxylase activities in cultured skin fibroblasts.

CONCLUSION

More attention should be paid to slight elevations of leucine levels in newborn mass screening. Urinary organic acid analysis should be performed in conspicuous cases.