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Propionic Acidemia

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Guidance for primary care clinicians receiving a positive newborn screen result

Other Names

Ketotic glycinemia
Ketotic hyperglycinemia
Propionyl-CoA carboxylase deficiency

ICD-10 Coding

E71.121, Propionic acidemia

Disorder Category

Organic acidemia

Screening

Abnormal Finding

Elevated C3 (propionyl carnitine)

Tested By

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

Description

Propionic acidemia is caused by a defect in the mitochondrial enzyme propionyl-CoA carboxylase, which is responsible for converting propionyl-CoA to methylmalonyl-CoA and subsequently to succinyl-CoA that enters the Krebs cycle. Propionyl-CoA carboxylase is involved in the catabolism of isoleucine, valine, methionine, and threonine, odd-chain fatty acids, cholesterol, and nucleotides. The defect results in the accumulation of propionic acid and its metabolites and a deficiency of the Krebs cycle with impaired energy production. Propionic acidemia is caused by a defect in either of two genes (PCCA and PCCB) that code for the alpha and beta subunits of the enzyme. Affected patients can present at a few days of life with progressive lethargy progressing to coma with severe metabolic acidosis and hyperammonemia. Some patients with milder mutations can present later in life with failure to thrive, vomiting, neurological symptoms (abnormal movements, seizures), and delays in development.

Clinical Characteristics

With treatment, normal development and IQ are possible for patients with milder variants, and symptomatic improvement may be seen in individuals already affected.
Without treatment, metabolic crises (severe metabolic acidosis with hyperammonemia) may lead to progressive neurologic injury and death. Symptoms generally begin within the first few days after birth, though in variant forms, they may not begin until after 6 weeks of age. Symptoms may be triggered by fasting and illness, and children may appear healthy between metabolic crisis episodes. Children with milder variants can present with neurological symptoms or cardiomyopathy without acute metabolic acidosis. The typical facies of infants with propionic acidemia includes: frontal bossing, widened depressed nasal bridge, epicanthal folds, long philtrum, upturned curvature of the lips.
Initial symptoms/signs may include:
  • Poor feeding
  • Vomiting
  • Seizures
  • Lethargy progressing to coma
  • Lab findings:
    • Metabolic acidosis
    • Hyperammonemia
    • Ketonuria
    • Neutropenia and thrombocytopenia
    • Elevated glycine (usually after the newborn period) in blood and presence of methylcitric acid in urine organic acids
If not treated promptly, recurrent metabolic crises may lead to:
  • Mental retardation
  • Movement disorders
  • Dystonia
  • Spasticity
  • Stroke
  • Brain damage
  • Death
Treatment consists of a low-protein diet, medical foods restricted of isoleucine, methionine, threonine and valine, odd-chain fatty acids and cholesterol, and carnitine supplements. Prompt treatment of illnesses and avoidance of fasting is necessary. Even with appropriate management, many patients have severe hypotonia and are developmentally delayed. Patients have an increased risk of infection, bone marrow suppression, cardiomyopathy, and recurrent pancreatitis. Older individuals can develop renal failure. Many children will need placement of a G-tube to facilitate feeding.
Liver transplantation can prevent metabolic crises, but its effect on chronic complications is still unclear. Novel therapies include using N-carbamylglutamate in hyperammonemic crises and chronic anaplerotic supplements (supplements that refill the Krebs cycle).

Incidence

The incidence for propionic acidemia is about 1:238,346. [Therrell: 2014]

Inheritance

Autosomal recessive

Other Testing

If the familial mutation is known, DNA testing is possible.

Primary Care Management

Next Steps After a Positive Screen

  • Contact the family and evaluate the infant for poor feeding, lethargy, vomiting, and tachypnea.
  • Provide emergency treatment/referral for symptoms of respiratory distress, metabolic acidosis, hypoglycemia, or seizures.
  • Discontinue breast or cow milk formula feeding.

Confirming the Diagnosis

  • To confirm the diagnosis, work with Newborn Screening Services (see NW providers [1]).
  • Follow-up testing may include quantitative plasma acylcarnitine profile, plasma amino acids, urine organic acids, plasma total homocysteine, and serum vitamin B12. The most common cause of elevated C3 (mild elevations) is maternal vitamin B12 deficiency.

If the Diagnosis is Confirmed

  • For evaluation and ongoing collaborative management, consult Biochemical Genetics (Metabolics) (see NW providers [1])
  • Refer for initial consultation and ongoing collaboration of dietary management. See Nutrition, Metabolic (see NW providers [13]).
  • Refer the family to Genetic Testing and Counseling (see NW providers [4]).
  • Educate the family regarding signs, symptoms, and the need for urgent care when the infant becomes ill. See Propionic Acidemia - Information for Parents (STAR-G).
  • Frequent low-protein, low-leucine, low-valine, low-methionine, low-threonine, and high-carbohydrate meals may be indicated for affected children (this will usually involve medical formulas and foods).
  • Avoid fasting; see the child promptly when illness causes poor intake.
  • Oral L-carnitine, antibiotics, and biotin may be indicated for some children.
  • Bicarbonate and glucose may be indicated during metabolic crisis episodes.
  • Monitoring of amino acid levels through blood and urine tests and ketones through urine tests may be indicated.
  • For those identified after irreversible consequences, assist in management, particularly with developmental and educational interventions.

Resources

Information & Support

After a Diagnosis or Problem is Identified
Families can face a big change when their baby tests positive for a newborn condition. Find information about A New Diagnosis - You Are Not Alone; Caring for Children with Special Health Care Needs; Assistance in Choosing Providers; Partnering with Healthcare Providers; Top Ten Things to Do After a Diagnosis.

For Professionals

Propionic Acidemia (GeneReviews)
Detailed information addressing clinical characteristics, diagnosis/testing, management, genetic counseling, and molecular pathogenesis; from the University of Washington and the National Library of Medicine.

Propionic Acidemia (OMIM)
Information about clinical features, diagnosis, management, and molecular and population genetics; Online Mendelian Inheritance in Man, authored and edited at the McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine

For Parents and Patients

Propionic Acidemia (MedlinePlus)
Information for families that includes description, frequency, causes, inheritance, other names, and additional resources; from the National Library of Medicine.

Propionic Acidemia - 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)
Clearinghouse for local, state, and national newborn screening education, programs, policies, and resources. Also, provides many ways for people to connect and share their viewpoints and questions about newborn screening, supported by the U.S. Department of Health and Human Services.

Center for Parent Information and Resources (DOE)
Parent Centers in every state provide training to parents of children with disabilities and provide information about special education, transition to adulthood, health care, support groups, local conferences, and other federal, state, and local services. See the "Find Your Parent Center Link" to find the parent center in your state; Department of Education, Office of Special Education.

Tools

ACT Sheet for Elevated C3 Acylcarnitine (ACMG) (PDF Document 352 KB)
Contains short-term recommendations for clinical follow-up of the newborn who has screened positive; American College of Medical Genetics.

Confirmatory Algorithms for Elevated C3 Acylcarnitine (ACMG) (PDF Document)
An algorithm of the basic steps involved in determining the final diagnosis of an infant with a positive newborn screen; American College of Medical Genetics.

Propionic Acidemia (NECMP)
A guideline for health care professionals treating the sick infant/child who has previously been diagnosed with propionic 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.

Services for Patients & Families Nationwide (NW)

For services not listed above, browse our Services categories or search our database.

* number of provider listings may vary by how states categorize services, whether providers are listed by organization or individual, how services are organized in the state, and other factors; Nationwide (NW) providers are generally limited to web-based services, provider locator services, and organizations that serve children from across the nation.

Studies

Propionic Acidemia in Children (ClinicalTrials.gov)
Studies looking at better understanding, diagnosing, and treating this condition; from the National Library of Medicine.

Helpful Articles

PubMed search for propionic acidemia in infants, last 3 years

Fraser JL, Venditti CP.
Methylmalonic and propionic acidemias: clinical management update.
Curr Opin Pediatr. 2016;28(6):682-693. PubMed abstract / Full Text

Vara R, Turner C, Mundy H, Heaton ND, Rela M, Mieli-Vergani G, Champion M, Hadzic N.
Liver transplantation for propionic acidemia in children.
Liver Transpl. 2011;17(6):661-7. PubMed abstract / Full Text
Study conclusion: LT has a role in the management of PA: it reduces the risk of metabolic decompensation and improves the quality of life. The potential for the development of metabolic sequelae is not completely eliminated.

Authors & Reviewers

Initial publication: March 2007; last update/revision: July 2017
Current Authors and Reviewers:
Author: Nicola Longo, MD, Ph.D.
Authoring history
2011: first version: Nicola Longo, MD, Ph.D.A
AAuthor; CAContributing Author; SASenior Author; RReviewer

Page Bibliography

Therrell BL Jr, Lloyd-Puryear MA, Camp KM, Mann MY.
Inborn errors of metabolism identified via newborn screening: Ten-year incidence data and costs of nutritional interventions for research agenda planning.
Mol Genet Metab. 2014;113(1-2):14-26. PubMed abstract / Full Text