Summary about Disease
Propionic acidemia (PA) is a rare inherited metabolic disorder that prevents the body from properly breaking down certain parts of protein and fats. This leads to a buildup of propionic acid and other harmful substances in the blood, which can damage organs and tissues, particularly the brain, heart, and liver. It is classified as an organic acidemia.
Symptoms
Symptoms vary in severity. In severe cases, newborns may exhibit:
Poor feeding
Vomiting
Lethargy
Seizures
Hypotonia (floppy muscle tone)
Enlarged liver (hepatomegaly)
High blood ammonia levels (hyperammonemia)
Coma Later-onset or milder cases may have:
Developmental delays
Intellectual disability
Poor growth
Chronic vomiting
Muscle weakness
Movement disorders
Heart problems (cardiomyopathy)
Causes
PA is caused by mutations in the PCCA or *PCCB* genes. These genes provide instructions for making parts (subunits) of the propionyl-CoA carboxylase enzyme. This enzyme is essential for breaking down certain amino acids (isoleucine, valine, threonine, and methionine), certain lipids, cholesterol, and odd-chain fatty acids. Mutations in these genes lead to a deficiency in the propionyl-CoA carboxylase enzyme.
Medicine Used
Treatment focuses on managing the symptoms and preventing complications. Medicines used include:
Low-protein diet: Restricts the intake of amino acids that break down into propionic acid.
Specialized medical formulas: Formulas low in specific amino acids are used to ensure proper nutrition while limiting problematic substances.
Carnitine: Helps to remove propionic acid from the body.
Antibiotics: May be used to treat bacterial overgrowth in the gut, which can contribute to propionic acid production.
Sodium benzoate/Sodium phenylbutyrate: Medications to reduce ammonia levels (hyperammonemia) in severe cases.
Biotin: A vitamin that can help some individuals with certain forms of the disease (biotin-responsive PA).
Liver Transplant: In severe cases where other treatment fails, liver transplantation may be an option.
Is Communicable
No, propionic acidemia is not communicable. It is a genetic disorder, meaning it is inherited from parents and cannot be spread from person to person.
Precautions
Strict adherence to dietary guidelines: Careful monitoring of protein intake and following a specialized diet is crucial.
Regular monitoring of blood ammonia levels: To detect and manage hyperammonemia.
Prompt treatment of infections: Illnesses can trigger metabolic crises.
Genetic counseling: For families with a history of PA, to assess the risk of having another affected child.
Newborn screening: Early detection through newborn screening programs can allow for early intervention and improved outcomes.
Emergency protocol: Families should have a plan in place for managing metabolic crises, including a list of medications and emergency contacts.
How long does an outbreak last?
Propionic acidemia does not have "outbreaks" in the traditional sense of an infectious disease. Instead, individuals with PA can experience metabolic crises, which are episodes of acute illness caused by a buildup of toxic substances. These crises can last for several days to weeks, depending on the severity and how quickly they are treated.
How is it diagnosed?
Diagnosis typically involves:
Newborn screening: Screening blood sample detects elevated propionylcarnitine levels.
Blood and urine tests: Detect elevated levels of propionic acid and related metabolites.
Enzyme assay: Measures the activity of propionyl-CoA carboxylase in skin fibroblasts or liver tissue.
Genetic testing: Identifies mutations in the PCCA or *PCCB* genes.
Timeline of Symptoms
Newborn period (Severe cases): Symptoms can appear within the first few days of life, including poor feeding, vomiting, lethargy, seizures, and coma.
Infancy and childhood (Milder cases): Symptoms may be less severe and appear later, such as developmental delays, poor growth, chronic vomiting, and muscle weakness.
Throughout life: Individuals with PA are at risk for metabolic crises throughout their lives, especially during times of stress, illness, or increased protein intake.
Important Considerations
Lifelong management: PA requires lifelong dietary management and monitoring.
Metabolic crises: Be aware of triggers for metabolic crises (infections, fasting, high protein intake) and have a plan for prompt treatment.
Developmental support: Children with PA may require early intervention and special education services.
Cardiomyopathy: Regular monitoring of heart function is important.
Neurological complications: Be aware of potential neurological complications, such as intellectual disability and movement disorders.
Family support: PA can be challenging for families, and support groups can provide valuable resources and connections.