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Malonyl-CoA decarboxylase deficiency
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

Malonyl-CoA decarboxylase deficiency

Malonyl-CoA decarboxylase deficiency is a rare metabolic disorder that prevents the body from converting certain fats into energy, often leading to developmental delays and heart complications.

Overview

Malonyl-CoA decarboxylase deficiency is a condition that prevents the body from converting certain fats into energy. Signs and symptoms typically appear in early childhood.

Common Symptoms

  • Delayed development
  • Weak muscle tone (hypotonia)
  • Seizures
  • Diarrhea and vomiting
  • Low blood sugar (hypoglycemia)
  • Cardiomyopathy (weakening and enlargement of the heart muscle)

Causes

Mutations in the MLYCD gene cause this deficiency. This gene provides instructions for making the enzyme malonyl-CoA decarboxylase, which helps regulate the formation and breakdown of fatty acids. Many tissues, including the heart, rely on fatty acids as a major energy source.

Mutations reduce or eliminate the function of this enzyme, disrupting the balance of fatty acid processing. This prevents the conversion of fats to energy and leads to the buildup of byproducts in tissues, contributing to the disorder's symptoms.

Inheritance

This condition is inherited in an autosomal recessive pattern, meaning both copies of the gene in each cell must have mutations. Parents of an affected individual typically carry one copy of the mutated gene but do not show signs or symptoms of the condition.

Frequently Asked Questions

Patients benefit from a high‑carbohydrate, low‑fat diet that limits long‑chain fatty acids (especially medium‑chain triglycerides) and provides frequent meals or continuous overnight feeds to avoid fasting. Supplementation with medium‑chain triglyceride‑free formulas, carnitine (if low), and careful monitoring of blood glucose are standard.
No enzyme‑replacement therapy exists yet, but aggressive metabolic management (diet, glucose infusion during illness) and cardiac support (ACE inhibitors, beta‑blockers) can stabilize heart function. Some centers trial riboflavin or bezafibrate to enhance residual enzyme activity, though evidence is limited. Early multidisciplinary care improves long‑term neurodevelopmental prognosis.
Typical red‑flag signs in the first year of life include poor weight gain, recurrent vomiting or diarrhea, episodes of low blood sugar, unexplained seizures, and a weak, floppy tone (hypotonia). The combination of metabolic crises with early‑onset cardiomyopathy should prompt metabolic work‑up.
Initial screening involves measuring elevated plasma malonyl‑CoA and abnormal acylcarnitine profiles (high C3‑OH). Definitive confirmation requires enzymatic activity testing in cultured fibroblasts or leukocytes and molecular genetic testing to identify biallelic pathogenic variants in the MLYCD gene.
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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