Table 4.

Teaching points

1.Genetic disorders presenting as rhabdomyolysis are rare and they usually present during childhood.

2.McArdle disease or glycogen storage disease type 5 is a type of metabolic myopathy caused by inherited pathogenic mutations in the PYGM gene leading to complete or partial absence of myophosphorylase enzyme.

3.Five features of McArdle disease necessary for the diagnosis are the following: exercise intolerance, muscle contractures, second-wind phenomenon, rhabdomyolysis/myoglobinuria, and additional investigations to confirm the diagnosis (baseline creatinine phosphokinase, uric acid levels, nonischemic forearm exercise test, genetic analysis and muscle biopsy).

4.Most beneficial intervention is a combination of aerobic conditioning and ensuring that sufficient blood glucose is constantly available to patients’ working muscles during the daytime.

5.Genetic sequencing of the parents and siblings is important to ascertain phase information and carrier status, respectively, for genetic counseling purposes.