Harun BAYRAK
Türkiye Çocuk Hastalıkları Dergisi - 2026;20(4):295-297
Maple syrup urine disease (MSUD) is an inborn error of metabolism characterized by an increase in branched-chain amino acids (BCAAs), resulting from a deficiency in the branched-chain alpha-ketoacid dehydrogenase (BCKD) enzyme. A 22-day-old asymptomatic male infant was referred to our center following the detection of elevated phenylalanine (PHE) levels in the newborn screening program and was hospitalized with suspected Phenylketonuria (PKU). Blood amino acid analysis revealed a normal PHE level (48.9 nmol/mL), while BCAA levels were markedly elevated: Leucine 824.4 nmol/mL (normal: 48-175), isoleucine 413.1 nmol/mL (normal: 31-105), and valine 683.1 nmol/mL (normal: 83-300). Results confirmed false positive result for PKU diagnosis however, laboratory findings were consistent with MSUD. Phenylketonuria, a preliminary diagnosis made due to high PHE levels in newborn screening, has masked the underlying MSUD diagnosis, and is presented here as an extremely rare phenomenon. This case is reported to underscore a critical gap in our country's newborn screening program, which does not currently include MSUD. Considering the acute and potentially fatal neonatal presentation of MSUD, our findings underline the need to expand the national newborn screening program to include MSUD.
