SynopsisCodesLook ForDiagnostic PearlsDifferential Diagnosis & PitfallsBest TestsManagement PearlsTherapyReferences
Juvenile polymyositis
Other Resources UpToDate PubMed

Juvenile polymyositis

Contributors: Joon B. Kim MD, Michael W. Winter MD, Paritosh Prasad MD
Other Resources UpToDate PubMed


This summary discusses polymyositis in children. Polymyositis in adults is addressed separately.

Juvenile polymyositis (JPM) is a diagnosis under a larger umbrella of juvenile idiopathic inflammatory myopathies (JIIMs). JPM involves T-cell invasion of muscle fibers. It has a prevalence of 2%-8% of all JIIMs, and it has a peak onset during adolescence.

It is characterized by proximal and distal muscle weakness, frequent falling episodes, myalgias, arthritis or arthralgias, and increased creatine kinase levels. Other associated symptoms include fevers, muscle atrophy, and dysphagia with palpitation in a minority of cases. Patients who have gastrointestinal involvement, periungal capillary changes, and Raynaud phenomenon likely have some overlap with scleroderma. JPM has clinical characteristics that are similar to juvenile dermatomyositis, but cutaneous findings such as Gottron's papules or heliotrope rash are absent. While muscle weakness is a central characteristic of JPM, up to 5% of patients will not have clinically evident weakness.

Muscle fibers of patients with JPM typically have endomysial lymphocytic infiltration; thus, a muscle biopsy is warranted in all cases in which JPM is suspected. Better delineation of the underlying abnormality in a variety of childhood inflammatory myopathies and improved diagnostic techniques have resulted in a reduction in the incidence of JIIMs that are diagnosed as JPM.


M33.20 – Polymyositis, organ involvement unspecified

738526005 – Juvenile polymyositis

Look For

Subscription Required

Diagnostic Pearls

Subscription Required

Differential Diagnosis & Pitfalls

  • Noninflammatory myopathy – see, eg, Duchenne muscular dystrophy, Limb-girdle muscular dystrophy
  • Juvenile dermatomyositis (JDM) – JDM will typically have cutaneous manifestations (heliotrope rash, Gottron's papules)
  • Metabolic myopathy – will typically have fatigue with exercise
  • Other etiologies of myopathy – viral (post-influenza, polio, etc) or due to other autoimmune conditions (Systemic lupus erythematosus, Scleroderma of childhood, Mixed connective tissue disease, and systemic Juvenile idiopathic arthritis)
  • Guillain-Barré syndrome (see Acute inflammatory demyelinating polyneuropathy)
  • Cerebral stroke
  • Transient ischemic attacks
  • Childhood stroke

Best Tests

Subscription Required

Management Pearls

Subscription Required


Subscription Required


Subscription Required

Last Reviewed:06/09/2019
Last Updated:04/26/2022
Copyright © 2024 VisualDx®. All rights reserved.
Juvenile polymyositis
A medical illustration showing key findings of Juvenile polymyositis : Arthralgia, Myalgia, CK increased, Unexplained falls
Copyright © 2024 VisualDx®. All rights reserved.