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Screening & Prevention >> Newborn Screening >> Organic Acidemias >> 2M3HBA

2M3HBA

Disorder Category

an organic acid disorder

Screening

Finding

elevated C5:1 (methylcrotonyl or tiglyl carnitine) and elevated C5-OH (3-hydroxyisovaleryl carnitine)

Tested By

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

Names

2M3HBA

2-methyl-3-hydroxybutyryl-CoA dehydrogenase deficiency

MHBD

hydroxyl-CoA dehydrogenase deficiency

3-hydroxy-2-methylbutyryl-CoA dehydrogenase deficiency

2-methyl-3-hydroxybutyric acidemia

ICD-9

270.3, Disturbances of branched-chain amino-acid metabolism

Overview

Deficiency of this mitochondrial enzyme results in impaired oxidation of certain fatty acids and isoleucine, with resultant accumulation of organic acids.

Prevalence

fewer than 10 reported cases [2M3HBA fact sheet, Iowa Dept. of Health]

Inheritance

X-linked, can affect females with a milder phenotype

Prenatal Testing

DNA and enzyme testing by amniocentesis or CVS.

Clinical Characteristics

With treatment, deterioration may be avoided, and some improvement may result. Without treatment, progressive loss of skills and neurologic impairment, mental retardation and seizures can be expected. Symptom onset has generally been between 9 and 14 months and may be aggravated by stress or illness.

Initial signs/symptoms may include:
  • poor feeding,
  • spasticity,
  • lethargy,
  • lab findings:
    • lactic acidosis.


If not treated promptly, patients may experience:
  • choreoathetosis,
  • progressive loss of motor skills,
  • hearing loss,
  • retinal degeneration,
  • seizures,
  • brain damage, and
  • death.

Follow-up on positive screening test

Quantitative plasma acylcarnitine profile, urine organic acids, enzyme assay in fibroblasts.

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;
  • Isoleucine and protein restriction, treatment of acute episodes with glucose and fluids;
  • For those identified after irreversible consequences, assist in management, particularly with low vision aids, hearing aids or cochlear implants, developmental and educational interventions.

Specialty Care Management

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

Resources

Links

For Professionals

ACT Sheet for 2M3HBA from ACMG
Developed by the American College of Medical Genetics (ACMG), includes recommended responses to positive newborn screening test results, diagnostic evaluation, clinical expectations, and sources of additional information. See the ACMG ACT Sheets and Confirmatory Algorithms (link elsewhere on this page) for more info and sheets on other conditions.

ACMG ACT Sheets and Confirmatory Algorithms
The American College of Medical Genetics (ACMG) has developed ACTion (ACT) Sheets and algorithms for responding to positive newborn screening test results. This page contains a table with links to all of the ACT Sheets and related algorithms.

2M3HBA, OMIM
From the Online Mendelian Inheritance in Man site, hosted by Johns Hopkins University, providing technical information for providers on genetic disorders, links to MEDLINE, and links to other scientific information and sites.

2M3HBA fact sheet, Iowa Dept. of Health
This fact sheet, developed by the Iowa Department of Health, provides information for parents and professionals.

For Parents

2M3HBA, Genetics Home Reference
Excellent, detailed review aimed at patients and families from the National Library of Medicine's Genetics Home Reference site.

Organic Acidemia Association (OAA)
A non-profit organization that provides information for parents and providers; newsletters; event information; connections with other parents; a listserv; a discussion board; information about nutrition and recipes; translation of their web pages into five other languages; hosting of the Propionic Acidemia Research Network and other research funds; and links to other sites.

Services

Newborn Screening Programs

Utah Newborn Screening Program, more info...
44 Mario Capecchi Drive
Salt Lake City, UT84114
Phone: 801-584-8256
Fax: 801-536-0966
http://health.utah.gov/newbornscreening

Pediatric Genetics

Metabolic Clinic, more info...
100 Mario Capecchi Drive
Salt Lake City, UT84113
Phone: 801-585-2457
Fax: 585-7252
http://www.ped.med.utah.edu/divisions/divisions.htm

See all Pediatric Genetics services providers (3) in our database.

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

Helpful Articles

PubMed search on 2M3HBA in the last 5 years.

Authors

Reviewing Author: Nicola Longo MD, PhD, 3/2007
Compiled and edited by: Alfred Romeo RN, PhD, 3/2007
Content Last Updated: 3/2008
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