Polymyositis

Annual incidence in USA: 5.5:1,000,000, most prevalent among black women

Annual incidence around the world: 1.9-7.7:1,000,000, although comprehensive epidemiologic data are lacking

Delayed recovery from muscle relaxation

Aspiration pneumonitis

Cardiac arrhythmias

CHF

Increased risk of aspiration

Respiratory muscle and/or diaphragmatic weakness

Hyperkalemia following succinylcholine use; sensitivity to NMB

Interstitial lung disease, progressive fibrosis, and/or difficulty with ventilation/oxygenation

Cardiomyopathy with heart failure

Chronic use of therapeutic steroids and anti-immunologic medications

Rare form of an acquired inflammatory myopathy affecting adults and rarely children.

Can often mimic many other myopathies and is a diagnosis of exclusion.

Pts present with progressive and symmetric proximal muscle weakness.

Diagnosis confirmed by analysis of serum muscle enzymes, EMG findings, and muscle biopsy (most definitive test).

A careful family history, medication list review, physical exam, blood test, and muscle biopsy are all crucial because they may help to exclude an alternative diagnosis, such as an inherited muscle disease or toxic myopathy.

An autoimmune etiology is suspected and hypothetically supported by an association with other autoimmune or connective tissue diseases and a response to immunotherapy.

Drugs—especially d -penicillamine, statins, or zidovudine—may also trigger an inflammatory myopathy.

Several viruses—including coxsackie, influenza, mumps, CMV, and Epstein-Barr virus—may also have an association.