McArdle Disease

Not yet reviewed

This information is AI generated and has not yet been reviewed by a specialist physician. AI can make mistakes.

Disease overview

Deficiency in the myophosphorylase enzyme (gene PYGM) impairs the ability to break down glycogen within muscle tissue specifically.

Common symptoms

Exercise intoleranceoften within first 10 years of life but can present at any age. Strenuous exercise induces muscle crampingfatiguerisk of rhabdomyolysis and myoglobinuria in severe disease. "Second wind phenomenon" where exercise tolerance improves after brief restor after prolonged moderate exericse.

When to suspect

  • Recommendation 1

    Initial screening with the ischemic forearm test is highly suggestive of disease

  • Recommendation 2

    Molecular testing for PYGM genetic mutation is preferred to confirm

  • Recommendation 3

    test available here. Assay of muscle myophosphorylase enzyme activity in a muscle biopsy sample may be considered if genetic testing is inconclusive

  • Recommendation 4

    this is an older test described here.

How to test

  • Recommendation 1

    Initial screening with the ischemic forearm test is highly suggestive of disease

  • Recommendation 2

    Molecular testing for PYGM genetic mutation is preferred to confirm

  • Recommendation 3

    test available here. Assay of muscle myophosphorylase enzyme activity in a muscle biopsy sample may be considered if genetic testing is inconclusive

  • Recommendation 4

    this is an older test described here.

ZebraMD is partnering with Ambry Genetics for clinical-grade whole genome testing for rare diseases. Ambry accepts insurance. If you don’t have a physician to order this test, join our referral list and our team will reach out.

Treatment

  • Recommendation 1

    Patients should be advised to follow a high-complex-carbohydrate diet

  • Recommendation 2

    extra carbohydrates should be consumed before planned exercise to help avoid rhabdomyolysis.

Primary care

  • Recommendation 1

    Annual physical exams and diet review/assistance. Promote regular exercise (with a supervised exercise program initially)

  • Recommendation 2

    patients who maintain physical activity have better prognosis.

Further support

  • Recommendation 1

    Several large academic medical centers have dedicated Glycogen Storage Disorder programs/clinics. Genetic counseling is recommended. The Scientific Advisory Board of the Association for Glycogen Storage Disease offers a list of hospitals with GSD-focused clinics.Referral to Medical Genetics Department, if available. Initial virtual care is also available through organizations like TeleRare Health.

Clinical trials

Clinical Trials

Sources

No data available

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