McArdle’s disease (or type V glycogenosis) is the most common metabolic myopathy. It is characterized by exercise intolerance with myalgia, cramps, muscle weakness. It is often accompanied by rhabdomyolysis, hyperCKemia and myoglobinuria, which can lead to acute renal failure.
A European register of muscular glycogenosis
The EUROMAC register was set up with the support of the European Union to collect data from patients with McArdle disease as well as other muscle glycogenoses such as glycogenoses type 0, III, IV, VII, VIII, IX, X, XI, XII, XIII, XIV and XV, with the exception of Pompe disease or type II glycogenosis which has its own register. From the inclusion of the first patient in 2015 until March 2018, complete data from 282 participants were collected, including 22 French participants. The vast majority of these patients (95.4%) had McArdle disease.
In McArdle’s disease
New phenotypic characteristics were highlighted following analysis of data from 269 patients with McArdle disease:
- a higher frequency (51.4%) of permanent muscle weakness than previously reported,
- a normal creatine kinase level (6.8%),
- ptosis (3%),
- a body mass index and a frequency of certain comorbidities (hypothyroidism, coronary heart disease, etc.) that are greater than in the general population.
The authors recommend watching for these less-known symptoms that can be overlooked. They also recommend not to exclude the diagnosis of McArdle disease if the creatine kinase level is normal and myoglobinuria absent.