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Tang, N. Short/Branched Chain Acyl-CoA Dehydrogenase Deficiency. Encyclopedia. Available online: (accessed on 30 May 2024).
Tang N. Short/Branched Chain Acyl-CoA Dehydrogenase Deficiency. Encyclopedia. Available at: Accessed May 30, 2024.
Tang, Nora. "Short/Branched Chain Acyl-CoA Dehydrogenase Deficiency" Encyclopedia, (accessed May 30, 2024).
Tang, N. (2020, December 25). Short/Branched Chain Acyl-CoA Dehydrogenase Deficiency. In Encyclopedia.
Tang, Nora. "Short/Branched Chain Acyl-CoA Dehydrogenase Deficiency." Encyclopedia. Web. 25 December, 2020.
Short/Branched Chain Acyl-CoA Dehydrogenase Deficiency

Short/branched chain acyl-CoA dehydrogenase (SBCAD) deficiency (also known as 2-methylbutyryl-CoA dehydrogenase deficiency) is a rare disorder in which the body is unable to process proteins properly.

genetic conditions

1. Introduction

Normally, the body breaks down proteins from food into smaller parts called amino acids. Amino acids can be further processed to provide energy for the body. People with SBCAD deficiency cannot process a particular amino acid called isoleucine.

Most cases of SBCAD deficiency are detected shortly after birth by newborn screening, which identifies abnormal levels of certain compounds in the blood. In individuals with this condition, a compound called 2-methylbutyryl carnitine is elevated in the blood and another called 2-methylbutyrylglycine is elevated in the urine (2-methylbutyrylglycinuria).

Most people with SBCAD deficiency have no health problems related to the disorder. A small percentage of affected individuals develop signs and symptoms of the condition, which can begin soon after birth or later in childhood. The initial symptoms often include poor feeding, lack of energy (lethargy), vomiting, and irritability. These symptoms sometimes progress to serious health problems such as difficulty breathing, seizures, and coma. Additional problems can include poor growth, vision impairment, learning disabilities, muscle weakness, and delays in motor skills such as standing and walking.

It is unclear why some people with SBCAD deficiency develop health problems and others do not. Doctors suggest that in some cases, signs and symptoms may be triggered by infections, prolonged periods without food (fasting), or an increased amount of protein-rich foods in the diet.

2. Frequency

SBCAD deficiency is a rare condition; its worldwide prevalence is unknown. This condition is most common among Hmong populations in Southeast Asia and in people of Hmong descent, affecting 1 in 250 to 1 in 500 people in these communities. These individuals do not usually develop health problems related to the condition.

3. Causes

Mutations in the ACADSB gene cause SBCAD deficiency. This gene provides instructions for making an enzyme called short/branched chain acyl-CoA dehydrogenase (SBCAD), which performs a chemical reaction that helps process the amino acid isoleucine. Mutations in the ACADSB gene reduce or eliminate the activity of this enzyme. With a shortage (deficiency) of SBCAD activity, the body is unable to break down isoleucine properly. Researchers speculate that some features of this disorder, such as lethargy and muscle weakness, occur because isoleucine is not converted to energy. In addition, impairment of SBCAD may allow the buildup of toxic compounds, which can lead to serious health problems.

4. Inheritance

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

5. Other Names for This Condition

  • 2-MBADD

  • 2-MBCD deficiency

  • 2-MBG

  • 2-methylbutyryl glycinuria

  • 2-methylbutyryl-CoA dehydrogenase deficiency

  • 2-methylbutyryl-coenzyme A dehydrogenase deficiency


  • short/branched-chain acyl-CoA dehydrogenase deficiency


  1. Alfardan J, Mohsen AW, Copeland S, Ellison J, Keppen-Davis L, Rohrbach M,Powell BR, Gillis J, Matern D, Kant J, Vockley J. Characterization of new ACADSB gene sequence mutations and clinical implications in patients with2-methylbutyrylglycinuria identified by newborn screening. Mol Genet Metab. 2010 Aug;100(4):333-8. doi: 10.1016/j.ymgme.2010.04.014.
  2. Andresen BS, Christensen E, Corydon TJ, Bross P, Pilgaard B, Wanders RJ,Ruiter JP, Simonsen H, Winter V, Knudsen I, Schroeder LD, Gregersen N, Skovby F. Isolated 2-methylbutyrylglycinuria caused by short/branched-chain acyl-CoAdehydrogenase deficiency: identification of a new enzyme defect, resolution ofits molecular basis, and evidence for distinct acyl-CoA dehydrogenases inisoleucine and valine metabolism. Am J Hum Genet. 2000 Nov;67(5):1095-103.
  3. Korman SH. Inborn errors of isoleucine degradation: a review. Mol Genet Metab.2006 Dec;89(4):289-99.
  4. Madsen PP, Kibaek M, Roca X, Sachidanandam R, Krainer AR, Christensen E,Steiner RD, Gibson KM, Corydon TJ, Knudsen I, Wanders RJ, Ruiter JP, Gregersen N,Andresen BS. Short/branched-chain acyl-CoA dehydrogenase deficiency due to anIVS3+3A>G mutation that causes exon skipping. Hum Genet. 2006 Feb;118(6):680-90.
  5. Matern D, He M, Berry SA, Rinaldo P, Whitley CB, Madsen PP, van Calcar SC,Lussky RC, Andresen BS, Wolff JA, Vockley J. Prospective diagnosis of2-methylbutyryl-CoA dehydrogenase deficiency in the Hmong population by newbornscreening using tandem mass spectrometry. Pediatrics. 2003 Jul;112(1 Pt 1):74-8. Review.
  6. Pasquali M, Monsen G, Richardson L, Alston M, Longo N. Biochemical findings incommon inborn errors of metabolism. Am J Med Genet C Semin Med Genet. 2006 May15;142C(2):64-76. Review.
  7. Sass JO, Ensenauer R, Röschinger W, Reich H, Steuerwald U, Schirrmacher O,Engel K, Häberle J, Andresen BS, Mégarbané A, Lehnert W, Zschocke J.2-Methylbutyryl-coenzyme A dehydrogenase deficiency: functional and molecularstudies on a defect in isoleucine catabolism. Mol Genet Metab. 2008Jan;93(1):30-5.
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