Short/branched chain acyl-CoA dehydrogenase deficiency

Disorder Category

An organic acidemia



Elevated C5 (isovaleryl carnitine)

Tested By

Tandem mass spectrometry (MS/MS); sensitivity=NA; specificity=NA


Short/branched chain acyl-CoA dehydrogenase deficiency



2-methylbutyryl CoA dehydrogenase deficiency

2MBCD deficiency


270.3, Disturbances of branched-chain amino-acid metabolism


Deficiency of 2-methylbutyryl-CoA dehydrogenase results in inability to break down isoleucine causing an organic acidemia. This condition is found mostly by newborn screening and its clinical significance is still unclear. Some of the initially reported patients had neurological symptoms, but their relationship to the metabolic defect remains unclear.


The condition is rare; less than 20 cases have been reported, primarily among the Hmong population. [Short/Branched Chain Acyl-CoA Dehydrogenase Deficiency - Information for Professionals (STAR-G)]


Autosomal recessive

Prenatal Testing

DNA testing or enzyme analysis by amniocentesis or CVS.

Clinical Characteristics

With treatment, limited experience suggests sequelae may be avoidable. Without treatment, acute neonatal decompensation with neurologic deficits has been described. Most infants and children will not display symptoms in this rare disorder. Symptoms may be triggered by fasting or illness.

Initial signs/symptoms may include:
  • Nausea
  • Vomiting
  • Irritability
  • Hypoglycemia
  • Lethargy

Treatment consists of carnitine supplementation and fasting avoidance. Again, the need for treatment is unclear and continued follow-up and monitoring of these patients seems at present the best course of action.

Follow-up Testing after Positive Screen

Quantitative plasma acylcarnitine profile, urine organic acids, urine acylglycine and acylcarnitine analysis. Urine acylglycine analysis is necessary to exclude this condition.

Primary Care Management

Upon Notification of the + Screen

If the Diagnosis is Confirmed

  • Educate the family regarding signs, symptoms, and the need for urgent care when the infant becomes ill (see Short/Branched Chain Acyl-CoA Dehydrogenase Deficiency - Information for Parents (STAR-G) for additional information).
  • Assist in implementation of a low protein diet and avoidance of fasting.
  • Oral L-carnitine may be indicated.
  • For those identified after irreversible consequences, assist in management, particularly with developmental and educational interventions.

Specialty Care Collaboration

Initial consultation and ongoing collaboration, particularly for dietary management. Genetic counseling for the family.


Information & Support

For Professionals

Isovaleric Acidemia Acute Illness Protocol (NECMP)
A guideline for health care professionals treating the sick infant/child who has previously been diagnosed with isovaleric acidemia; developed under the direction of Dr. Harvey Levy, Senior Associate in Medicine/Genetics at Children’s Hospital Boston, and Professor of Pediatrics at Harvard Medical School, for the New England Consortium of Metabolic Programs.

Short/Branched Chain Acyl-CoA Dehydrogenase Deficiency - Information for Professionals (STAR-G)
On the Screening, Technology and Research in Genetics (STAR-G) site, one of a series of Disorder Fact Sheets for Professionals; structured list of information about the condition, with links to more information.

Short/Branched Chain Acyl-CoA Dehydrogenase (OMIM)
Extensive review of literature that provides technical information on genetic disorders; Online Mendelian Inheritance in Man site, hosted by Johns Hopkins University.

Newborn Screening ACT Sheets & Confirmatory Algorithms (ACMG)
ACTion (ACT) Sheets and algorithms for responding to positive newborn screening test results, membership required; American College of Medical Genetics.

Newborn Screening Information for Clinicians (NNSGRC)
Fact sheets, data reports, publications ,and information for clinicians about genetic screening that includes links to state genetic contacts; National Newborn Screening & Global Resource Center.

Genetics in Primary Care Institute (AAP)
The goal of this site is to increase collaboration in the care of children with known or suspected genetic disorders. Includes health supervision guidelines and other useful resources; a collaboration among the Health Resources & Services Administration, the Maternal and Child Health Bureau, and the American Academy of Pediatrics.

Orphanet is a consortium involving over 40 countries and coordinated in France to provide a portal for information about rare diseases and orphan drugs.

Utah Newborn Screening Program (UDOH)
Provides information about the program, related legislation, training for practices, and newborn conditions; Utah Department of Health.

For Parents and Patients

2-methylbutyryl-CoA Dehydrogenase Deficiency (Genetics Home Reference)
Also known as short/branched chain acyl-CoA dehydrogenase deficiency. Excellent, detailed review of condition for patients and families; U.S. National Library of Medicine.

Short/Branched Chain Acyl-CoA Dehydrogenase Deficiency - Information for Parents (STAR-G)
A fact sheet, written by a genetic counselor and reviewed by metabolic and genetic specialists, for families who have received an initial diagnosis of this newborn disorder; Screening, Technology and Research in Genetics.

Baby's First Test (Genetic Alliance)
A clearinghouse for newborn screening information. Provides resources about screening at the local, state, and national levels and ways for people to share their viewpoints and questions about newborn screening.

Newborn Screening Information For Families (NNSGRC)
Information for families about genetic screening; links to support groups, advocacy groups, and state genetic contacts; newsletters; factsheets; data reports; and publications; National Newborn Screening and Global Resource Center.

Organic Acidemia Association (OAA)
A nonprofit organization that provides information, newsletters, calendars of events, connections with other parents, a listserv, a discussion board, and nutrition and recipe ideas.

Utah Parent Center
A non-profit organization that provides training, information, referral, and assistance to parents of children and youth with all disabilities including physical, mental, hearing, vision, learning, behavioral, and emotional. Staff consists primarily of parents of children and youth with disabilities.

Center for Parent Information and Resources (DOE)
A large resource library related to children with disabilities. Parent Centers in every state provide training to parents of children with disabilities. Lists local conferences, support groups, advocacy tips, and suggestions for finding schools and other local services; Department of Education, Office of Special Education.


ACT Sheet for Elevated C5 Acylcarnitine (Biotinidase) (ACMG) (PDF Document 348 KB)
Contains short-term recommendations for clinical follow-up of the newborn who has screened positive; American College of Medical Genetics.


Genetics-related clinical services throughout the world can be found through Genetics Clinic Directory (GeneTests).

Newborn Screening Programs

See all Newborn Screening Programs services providers (3) in our database.

Pediatric Genetics

See all Pediatric Genetics services providers (5) in our database.

For other services related to this condition, browse our Services categories or search our database.

Helpful Articles

PubMed search for short/branched chain acyl-CoA dehydrogenase deficiency and neonatal screening, last 5 years.

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 with 2-methylbutyrylglycinuria identified by newborn screening.
Mol Genet Metab. 2010;100(4):333-8. PubMed abstract / Full Text
These findings confirm that SBCAD deficiency can be identified through newborn screening by acylcarnitine analysis. Our patients have been well without treatment and call for careful follow-up studies to learn the true clinical impact of this disorder.


Reviewing Author: Nicola Longo, MD, PhD - 7/2011
Compiled and edited by: Alfred Romeo, RN, PhD - 3/2007
Content Last Updated: 7/2011