2M3HBA Deficiency
Other Names
2-methyl-3-hydroxybutyryl-CoA dehydrogenase deficiency
MHBD deficiency
hydroxyl-CoA dehydrogenase deficiency
3-hydroxy-2-methylbutyryl-CoA dehydrogenase (3H2MBD) deficiency
2-methyl-3-hydroxybutyric acidemia
Screening
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 Deficiency Fact Sheet (Iowa Dept. of Health) (
21 KB)]
Prenatal Testing
DNA testing possible by amniocentesis or chorionic villus sampling (CVS) if both disease causing mutations of an affected family member have been identified. Enzyme testing possible by amniocentesis or CVS.Other Testing
Genetic testing is possible for at-risk family members if both disease causing mutations of an affected family member have been identified.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
- Choreoathetosis
- Progressive loss of motor skills
- Hearing loss
- Retinal degeneration
- Seizures
- Brain damage
- Death
Follow-up Testing after Positive Screen
Quantitative plasma acylcarnitine profile, urine organic acids, enzyme assay in fibroblasts.Primary Care Management
Upon Notification of the + Screen
- Contact the family and evaluate the infant for poor feeding, vomiting, or lethargy.
- Provide emergency treatment/referral for symptoms of hypoglycemia, metabolic acdosis, or seizures.
- To confirm the diagnosis, work with the following service(s): we currently have no Newborn Screening Programs service providers listed, please search our Services database for related services.
- For evaluation and ongoing collaborative management, consult the following service(s): we currently have no Pediatric Genetics service providers listed, please search our Services database for related services.
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 Collaboration
Initial consultation and ongoing collaboration, particularly for dietary management. Genetic counseling for the family.Resources
Information & Support
For Professionals
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.
Resources for 2M3HBA Deficiency (Disease InfoSearch)
Compilation of information, articles, research, case studies, and genetics links; from Genetic Alliance.
2M3HBA Deficiency (OMIM)
Extensive review of literature that provides technical information on genetic disorders; Online Mendelian Inheritance in Man
site, hosted by Johns Hopkins University.
2M3HBA Deficiency Fact Sheet (Iowa Dept. of Health) ( 21 KB)
Provides information for parents and professionals.
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. It includes
health supervision guidelines and other useful resources; represents a collaboration among the Health Resources & Services
Administration, the Maternal and Child Health Bureau, and the American Academy of Pediatrics.
For Parents and Patients
Support
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.
General
2M3HBA Deficiency (Genetics Home Reference)
Excellent, detailed review of condition for patients and families; U.S. National Library of Medicine.
National Newborn Screening & Global Resource Center (NNSGRC)
Fact sheets, data reports, publications, and information for clinicians about genetic screening that includes links to state
genetic contacts.
Tools
ACT Sheet for Elevated C5-OH Acylcarnitine (ACMG) ( 400 KB)
Contains short-term recommendations for clinical follow-up of the newborn who has screened positive; American College of Medical
Genetics.
Services
Newborn Screening Programs
We currently have no Newborn Screening Programs service providers listed; search our Services database for related services.
Pediatric Genetics
We currently have no Pediatric Genetics service providers listed; search our Services database for related services.
For other services related to this condition, browse our Services categories or search our database.
Authors
| Author: | Nicola Longo, MD, PhD - 3/2007 |
| Reviewing Author: | Kimberly Hart, MS, LCGC - 6/2012 |
| Compiled and edited by: | Alfred Romeo, RN, PhD - 3/2007 |
| Content Last Updated: | 6/2012 |