How do you diagnose Juvenile Polymyositis?

And how do you differentiate it between other juvenile idiopathic inflammatory myopathies?

A young patient presents with progressive symmetrical proximal weakness. Over the span of a couple months, the patient goes from achieving normal developmental milestones to near complete paralysis requiring mechanical ventilation.

The patient is discovered to have juvenile polymyositis, a rare idiopathic inflammatory myopathy. It’s only differentiating symptom between juvenile polymyositis (JPM) and juvenile dermatomyositis (JDM) is that the latter presents with cutaneous symptoms, like Gottron’s rash or heliotrope rash. JPM has no cutaneous symptoms.

Diagnosing JPM is primarily done by exclusion, and can be differentiated from other congenital myopathies by its subacute onset. MRI is now the first choice for confirming diagnosis, as inflammation appears as bright spots on T2 weighted images.

The goal of treatment is to stop the progression of muscle inflammation using glucocorticoids and steroid-sparing agents like methotrexate or cyclosporine. Some patients may fully recover, while others may relapse, or experience chronic symptoms for the rest of their lives.

-- Chapters --
0:00 Case Description
0:32 Vitals and Physical Exam
2:31 Diagnostic Results
4:31 Treatment
5:00 Conclusion

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[fibergeek]

What about antibodies for polymyositis do juveniles test positive for those as well?