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Mitochondrial trifunctional protein deficiency
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

Mitochondrial trifunctional protein deficiency

Mitochondrial trifunctional protein deficiency is a rare metabolic disorder that prevents the body from converting certain fats into energy, particularly during fasting or illness.

Overview

This condition prevents the body from breaking down long-chain fatty acids, which are a vital energy source for the heart, muscles, and liver. Symptoms can be triggered by fasting or viral infections and may be mistaken for Reye syndrome.

Symptoms

Infants may experience:

  • Feeding difficulties and lethargy
  • Low blood glucose (hypoglycemia)
  • Weak muscle tone (hypotonia)
  • Liver problems
  • Serious heart complications and breathing difficulties

Symptoms appearing after infancy may include muscle pain, breakdown of muscle tissue, and peripheral neuropathy (loss of sensation in the extremities).

Causes

The condition is caused by mutations in the HADHA or HADHB genes. These genes provide instructions for the mitochondrial trifunctional protein, an enzyme complex required to metabolize long-chain fatty acids. When this complex is deficient, the body cannot convert these fats into energy, leading to hypoglycemia and lethargy. Furthermore, the buildup of unprocessed fatty acids can become toxic, damaging the liver, heart, and muscles.

Inheritance

Mitochondrial trifunctional protein deficiency is inherited in an autosomal recessive pattern. An affected individual must inherit two mutated copies of the gene—one from each parent. The parents are typically carriers who do not display symptoms of the disorder.

Frequently Asked Questions

Initial screening includes a plasma acylcarnitine profile showing elevated long‑chain 3‑hydroxy‑acylcarnitines and a urine organic acid analysis with increased dicarboxylic acids. Definitive diagnosis requires molecular testing for pathogenic variants in HADHA or HADHB. For ongoing monitoring, check fasting blood glucose, serum CK (muscle breakdown), liver transaminases, and cardiac enzymes during intercurrent illness; periodic echocardiograms assess cardiac function.
During illness, the body’s demand for energy rises while intake may fall, increasing the risk of hypoglycemia and fatty‑acid buildup. Keep a regular schedule of frequent, carbohydrate‑rich meals or oral glucose gels (e.g., 10 g glucose every 2–3 hours). If the child cannot tolerate oral intake, seek emergency medical care for intravenous dextrose. Avoid prolonged fasting (no more than 4–6 hours) and have a written emergency plan with your pediatric metabolic team.
diet low in long‑chain fatty acids and high in medium‑chain triglycerides (MCT oil) is standard because MCTs bypass the defective step and can be oxidized for energy. Limit foods rich in long‑chain fats (e.g., butter, oils, fatty meats) and provide a balanced intake of carbohydrates and protein. Some centers also prescribe a “MCT‑enriched formula” for infants. Regular nutritionist follow‑up is essential to ensure growth and prevent essential fatty‑acid deficiency.
There is no cure, but early detection and metabolic control reduce organ damage. Cardiac involvement is managed with standard heart‑failure therapies (ACE inhibitors, beta‑blockers) and regular cardiac imaging. For muscle pain or rhabdomyolysis, avoid strenuous exercise, ensure prompt glucose supplementation, and monitor CK levels. Experimental therapies such as riboflavin or bezafibrate have been tried in isolated cases, but evidence is limited; treatment decisions should be made with a metabolic specialist.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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