Dermatomyositis

Prevalence in USA: 3000–10,000.

Group, demographics with highest prevalence include females, 2:1 relative to men, with a peak onset between 30–60 y of age.

Increased risk of respiratory failure and infections postop

Most case reports absolutely avoid depolarizing muscle relaxants and are careful with medications that have effects on muscle strength.

Monitor muscle relaxant dosing and recovery.

Valvular heart disease and cardiomyopathy: Cardiac muscle, though not severely involved, shows changes similar to skeletal muscles. Clinical manifestations are rare.

Relatively rare diffuse connective tissue disorder of uncertain etiology characterized by idiopathic inflammatory myopathy with muscle involvement and weakness muscle and connective tissue involvement of skin and other organs. Valvular heart disease increases the risk of periop adverse cardiac events.

Diagnosis is based on the clinical picture of muscle weakness and skin rash, myelography, raised serum CPK levels, and muscle biopsy.

Respiratory system: Aspiration pneumonia may occur due to weakness of the muscle involved in swallowing. Progressive weakness of the intercostal and diaphragmatic muscles may result in respiratory insufficiency. Lung involvement may occur from the connective tissue disorder itself, which results in patchy infiltrates throughout both lungs, interstitial pneumonia, or fibrosis. Carcinoma of the bronchus or lung parenchyma is associated.

The lead theory regarding dermatomyositis involves a genetic predisposition to viral or immune destruction of muscles by viruses or other infectious agents. Dermatomyositis is considered a connective tissue diseases in the same category as lupus erythematosus or systemic sclerosis.