Myopathies related to glycogen metabolism disorders [21 genes]

Metabolic myopathies are a group of secondary hereditary muscle diseases of enzymatic defects that affect the metabolic process and production of muscle energy. Some of them are considered to be inborn errors of metabolism and, even though they are rare causes of myopathy, their diagnostic importance lies in that some of them are potentially treatable.

Symptomatology may be similar to other forms of muscular dystrophy or inflammatory myopathies, usually with subtle symptoms, such as asymptomatic elevation of CPK, muscle cramps, myalgia, or myoglobinuria. Their prevalence is unknown: Pompe disease (acid maltase deficiency) affects 1 in 40,000 and McArdle disease 1 in 100,000 individuals.

Their etiology is related to problems in the metabolism of glycogen, lipids, or mitochondrial oxidation. Because of this, we have designed three specific panels for each metabolic pathway and a comprehensive panel that contemplates all of the implicated genes as a whole.

• GAA: Pompe disease (Glycogenosis type II)
• PYGM: McArdle disease (Glycogenosis type V)
• LAMP2: Danon disease
• PFKM: Muscle phosphofructokinase deficiency (Glycogenosis type VII)
• GYG1 / RBCK1: Myopathy due to polyglucosan bodies
• AGL / GBE1: Deficiency of glycogen branching/debranching enzyme
• PGAM2: Phosphoglycerate mutase deficiency (Glycogenosis type X)
• PGK1: Phosphoglycerate kinase deficiency
• PGM1: Glycosylation congenital disorder type I
• PHKA1 / PHKA2 / PHKB / PHKG2: Phosphorylase kinase deficiency (Glycogenosis type IX)
• LDHA: Lactate dehydrogenase deficiency (Glycogenosis type XI)
• ENO3: Enolase deficiency type III