McArdle's disease: case report

*Correspondence: [e-mail].

Abstract

Case Presentation: Female schoolchild, daughter of a non-consanguineous couple, without relevant prenatal history, with normal neuropsychomotor development. She presents recurrent clinical picture of fatigue on medium and great efforts since early childhood. At 8 years old, develops an urticarial rash and angioedema of the eyelids and lips, evolving with edema of the lower limbs up to the ankle, pain and difficulty to walk, requiring hospitalization, where an increase in CK (34.027 IU/L) and CK-MB (1298 IU/L) was seen, in addition to positive RT-PCR Covid. She was hospitalized for 5 days for venous hydration and was discharged asymptomatic. Sporadically complained of diffuse pain and fatigue in the upper and lower limbs after moderate to intense physical exertion, which improved with rest. After 2 years, was admitted again for cervicalgia and diffuse pain in the upper limbs with edema of the biceps muscles and increased TGO, TGP, LDH, and CK. After the second episode, she sought treatment from a rheumatologist, who showed an increase in CPK and excluded rheumatologic causes for the muscular crises. Currently, at the age of 10, maintains fatigue after physical exercise, with no limitation to daily activities and a normal intercrisis neurological physical examination. Given the clinical picture, a genetic panel was requested, and a pathogenic variant was found in homozygosity in the PYGM- McArdle's disease gene.

Discussion: McArdle's disease (glycogenase type V - GSD) is characterized by complete deficiency/absence of the enzyme myophosphorylase, autosomal recessive origin caused by mutations in the PYGM gene. First symptoms occur in childhood and manifest with exercise intolerance, cramps, fatigue, and muscle weakness. A phenomenon known as 'second wind' is observed in many patients with relief of myalgia and fatigue after few minutes of rest. This clinical picture is usually standard, but some patients may manifest moderate or severe forms, with rhabdomyolysis and myoglobinuria. The diagnosis is made by muscle biopsy, showing deficiency of myophosphorylase activity, or by genetic testing.

Final Comments: The report of this case intends to make known a rare disease and alerts to the importance of the appreciation of certain complaints, even if nonspecific, they should be better explored. Unfortunately, there is no established treatment, in general, the recommendation is a diet rich in carbohydrates and low in fats, in addition to orienting the performance of less intense exercises with little load.

 

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Publication History

Article published online:
12 May 2025