Myoadenylate deaminase deficiency is one of the most common causes of metabolic myopathy. It affects 1 to 2% of the European population, although in most people it does not cause any symptoms.
Myoadenylate deaminase (AMPD1 gene)
Myoadenylate deaminase deficiency (MAD) is a form of myopathy of a metabolic nature characterized by myalgia or muscle pain after exertion and reduced exercise tolerance. Inherited cases are mainly caused by variants in the AMPD1 gene (the most frequent being C34T or c.34C>T), and follow an autosomal recessive mode of inheritance with incomplete penetrance. This means that not all people who have two copies of a variant in AMPD1 causing the deficiency become symptomatic.
The function of the enzyme myoadenylate deaminase is to convert adenosine monophosphate to inosine monophosphate and ammonia as part of purine nucleotide metabolism. This metabolic pathway is essential for energy production in skeletal muscle cells.
Since MAD usually causes mild symptoms in a small proportion of patients, it is questionable whether it has clinical relevance. However, recent studies suggest that it may have a deleterious impact on athletic performance. On the other hand, there are studies suggesting that MAD-related variants may even have a cardioprotective effect in patients with heart failure.
Genes analyzed
Bibliography
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