Muscle Weakness Abnormal Gait or Difficulty Walking Elevated Creatine Kinase Respiratory Insufficiency Difficulty Swallowing Exercise Intolerance
2.7 to 70 per 100,000
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Pompe disease
2.5 per 100,000
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  • Polymyositis is an inflammatory myopathy that causes chronic inflammation and weakness in the skeletal muscles of the upper arms and legs
  • Signs and symptoms of polymyositis may overlap with Pompe disease

Signs and Symptoms

  • Similar to Pompe disease, patients with polymyositis generally experience weakness in the proximal musculature, including the muscles of the upper arms, shoulder, upper legs, and hip
  • The symptoms may worsen over time, and muscles farther away from the abdomen, such as those in the lower arms and legs, hands, and feet, may become affected
    • Common to the experiences of some patients with Pompe disease, symptoms of muscle weakness include difficulty standing from a seated position, climbing stairs, lifting objects, or raising the arms above the head
  • Patients with polymyositis may also experience fatigue, muscle or joint tenderness that is mild, swallowing or speaking difficulties, shortness of breath, heart arrhythmias, and arthritis


  • Unlike in Pompe disease, it is not known if polymyositis is caused by mutations in a specific gene
  • Some tests commonly used in the diagnostic pathway for Pompe disease are typically employed in the investigation of polymyositis, and include electromyography and laboratory testing (e.g., creatine kinase)
  • Polymyositis differs from Pompe disease as its diagnosis is aided by detection of autoantibodies specific to an associated autoimmune response

The information presented is intended as a brief overview. It is not an exhaustive summary of polymyositis. For more information on polymyositis, visit: https://rarediseases.info.nih.gov/diseases/7425/polymyositis

For more information on the diagnosis of Pompe disease, visit Diagnosis of Infantile-Onset Pompe Disease and Diagnosis of Late-Onset Pompe Disease