Propionic acidemia

Disease Description (Causes and Symptoms)

• Definition and cause: Propionic acidemia (propionic acidemia) is a rare genetic disorder in which propionic acid and related metabolites accumulate due to dysfunction of the propionyl-CoA carboxylase enzyme. It is primarily inherited in an autosomal recessive manner and is caused by mutations in the gene encoding the enzyme.
• Pathophysiology: Due to the enzyme deficiency, branched-chain amino acids (valine, isoleucine), methionine, threonine, and some fatty acid/corenstant metabolites are not properly processed, leading to the accumulation of toxic intermediate metabolites and resulting in metabolic acidosis, hyperammonemia, and reduced energy production.
• Main symptoms (clinical manifestations):
  • Neonatal period: vomiting, feeding difficulty, poor appetite, dehydration, rapid breathing (signs of metabolic acidosis), possible coma
  • Bleeding tendency (petechiae due to thrombocytopenia) and increased risk of infection due to leukopenia
  • Ketonuria/ketonemia, hypoglycemia, hyperammonemia
  • Chronic phase: growth retardation, developmental delay, intellectual disability, seizures, neurological damage (such as movement disorders)
  • Other complications may include cardiomyopathy, pancreatitis, and, occasionally, retinal or optic nerve abnormalities

Treatment (Standard Treatment, Medications, Lifestyle Management, and Precautions)

• Acute phase (during metabolic decompensation)
  • Immediate fasting (discontinuation of oral intake) and intravenous fluids (including glucose) to provide energy and halt protein intake
  • Correction of acidosis (such as with bicarbonate) and electrolyte correction
  • Treatment to remove ammonia in cases of hyperammonemia (ammonia-scavenging agents [e.g., sodium benzoate/phenylbutyrate], and hemodialysis in severe cases)
  • Treatment of infection, dehydration, and stress-related factors that worsen the condition
• Long-term management
  • A protein-restricted diet (especially restricting valine, isoleucine, methionine, and threonine), with the use of special formula/nutritional supplements to minimize the production of residual metabolites
  • Adequate carbohydrate and calorie intake to prevent protein breakdown (fasting should be avoided)
  • Cofactor supplementation: L-carnitine (used as standard; example dose 50–100 mg/kg/day, as directed by a physician), and biotin supplementation when necessary (used in some patients)
  • Oral administration of antibiotics to suppress intestinal propionic acid production (such as neomycin or metronidazole) (short-term, as directed by a physician)
  • Regular testing (blood and urine organic acids, amino acids, cardiac evaluation, etc.) and developmental/nutritional management
  • In some patients, liver transplantation (or combined liver-kidney transplantation) may be considered to improve metabolic control and reduce recurrent acute exacerbations (consult a specialist regarding indications and risks)
• Lifestyle management and precautions
  • Prepare a “metabolic crisis (sick-day) plan” for fasting or stressful situations such as fever and vomiting, and contact the hospital immediately
  • Make advance preparations for situations that may worsen metabolism, such as infections, surgery, and childhood vaccinations
  • Carry an emergency card containing available emergency treatments and contact information (including a diagnosis and treatment summary)
  • Long-term monitoring of growth and development and rehabilitation (such as physical and speech therapy)
• Risk of complications
  • Neurological damage (intellectual disability, seizures), cardiomyopathy, pancreatitis, recurrent metabolic crises, life-threatening hyperammonemia, etc.

Outpatient Visit Checklist (Including Items to Prepare and Sample Questions)

• Items to prepare (things to bring)
  • List of currently used medications and nutritional supplements and their doses (medication packaging, if possible)
  • Recent hospital records and test results (blood tests, organic acid test results, genetic test results, etc.)
  • Growth chart (weight and height) and diet/feeding records (daily intake, special formula/nutritional supplements currently being used)
  • Record of recent symptom changes (the timing and frequency of vomiting, decreased appetite, fever, seizures, etc.)
  • Emergency contact information and previous hospitalization and treatment history
• Situations to tell the doctor about in advance during the outpatient visit
  • Vomiting, fever, or dehydration symptoms within the past several days
  • Newly started medications or supplements
  • Whether vaccination or surgery is scheduled

General Sample Questions to Ask the Doctor

• "What is the purpose of the currently prescribed medication (or supplement), and what are its possible side effects?"
• "What is the expected prognosis, and what complications should be monitored over the long term?"
• "What should I be careful about in daily life (meals, exercise, school, etc.)?"
• "What emergency response procedures should be followed immediately in an emergency (if vomiting or fever occurs)?"

Disease-Specific Sample Questions

• "Based on the patient's current blood amino acid and organic acid test results, what is the allowable daily protein (or specific amino acid) intake? What supplements would you recommend if necessary?"
• "There has been a history of recurrent metabolic deterioration. Is liver transplantation (or another treatment) an appropriate option, and what are the expected benefits and risks?"

(Note: The information above has been compiled based on general medical knowledge. Diagnosis and treatment plans may vary depending on each patient's condition, so please consult the responsible specialist.)