J Genet Med.  2014 Jun;11(1):22-26. 10.5734/JGM.2014.11.1.22.

Identification of Two Novel BCKDHB Mutations in Korean Siblings with Maple Syrup Urine Disease Showing Mild Clinical Presentation

• Ko JM
• Shin CH
• Yang SW
• Cheong HI
• Song J

• KMID: 1737959
• DOI: http://doi.org/10.5734/JGM.2014.11.1.22

Abstract

Maple syrup urine disease (MSUD) is a disorder that involves the metabolism of branched chain amino acids, arising from a defect in branched-chain alpha-keto acid dehydrogenase complex. Mutations have been identified in the BCKDHA, BCKDHB, or DBT genes, which encode different subunits of the BCKDH complex. Although encephalopathy and progressive neurodegeneration are its major manifestations, the severity of the disease may range from the severe classic type to milder intermediate variants. We report two Korean siblings with the milder intermediate MSUD who were diagnosed with MSUD by a combination of newborn screening tests using tandem mass spectrometry and family genetic screening for MSUD. At diagnosis, the patients' plasma levels were elevated for leucine, isoleucine, valine, and alloisoleucine, and branched-chain alpha-keto acids and branched-chain alpha-hydroxy acids were detected in their urine. BCKDHA, BCKDHB, and DBT analysis was performed, and two novel mutations were identified in BCKDHB. Our patients were thought to have the milder intermediate variant of MSUD, rather than the classic form. Although MSUD is a typical metabolic disease with poor prognosis, better outcomes can be expected if early diagnosis and prompt management are provided, particularly for milder forms of the disease.

Keyword

Maple syrup urine disease; BCKDHB; Novel mutation; Korean

MeSH Terms

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)
Amino Acids
Diagnosis
Early Diagnosis
Genetic Testing
Humans
Infant, Newborn
Isoleucine
Leucine
Maple Syrup Urine Disease*
Mass Screening
Metabolic Diseases
Metabolism
Plasma
Prognosis
Siblings*
Tandem Mass Spectrometry
Valine
3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)
Amino Acids
Isoleucine
Leucine
Valine