What is propionic acidemia?

Propionic acidemia is a rare inherited condition in which the body is unable to break down certain proteins and fats. Symptoms most commonly show up during the first weeks of life. In some affected infants, episodes of symptoms may alternate with periods of seemingly normal health.

Without appropriate treatment, episodes of vomiting, lethargy, dehydration, and accumulation of excessive levels of acids in the blood and bodily tissues can lead to coma and death. If the condition is identified early in life and proper treatment begins, the early complications of the condition can be minimized

Causes

Propionic acidemia is caused by changes (mutations) in two genes, PCCA and PCCB, resulting in a deficiency of an enzyme that is required for the proper breakdown of certain amino acids. These amino acids are needed for proper growth and development. Other substances that are necessary for the body’s metabolic processes also do not properly break down, leading to the accumulation of toxic chemicals in the body.

Propionic acidemia is inherited in an autosomal recessive manner. Every person receives two copies of each of the two genes associated with propionic acidemia. In order to be affected with propionic acidemia, an individual needs to have two disease-causing genetic variants in the same gene; one in the copy of the gene they inherit from their mother and the other variant in the copy of the gene they inherit from their father.

Symptoms

Symptoms most commonly develop during the first weeks of life and may include:

• vomiting
• listlessness (lethargy)
• low muscle tone (hypotonia)
• failure to grow and gain weight at the expected rate (failure to thrive)
• dehydration

Many of these symptoms are the result of a baby eating foods that their body cannot break down.

How is propionic acidemia diagnosed?

Propionic acidemia can be identified at birth through newborn screening. Additional testing to confirm a diagnosis in an asymptomatic newborn with an abnormal newborn screen or in a symptomatic individual include:

• Gene sequencing of the PCCA and PCCB genes
• Blood and urine testing to assess for markers of the condition

Treatment

Children with propionic acidemia must follow a diet low in protein and certain fats. Specific food formulas can be used for a child’s diet. They must often be seen by a metabolic physician to manage long-term and acute care needs. Antibiotics usually need to be taken regularly.

Liver transplant is a surgical option that can help decrease the frequency of acute metabolic episodes.

Long-term outlook

A person with propionic acidemia needs to follow a carefully monitored diet for their lifetime. Affected individuals require lifelong follow-up with multiple specialists.