Dermatomyositis

Dermatomyositis and polymyositis are idiopathic chronic inflammatory diseases of the striated muscles. They are manifested by symmetrical muscle weakness, mainly in the proximal part of the upper and lower limbs. Dermatomyositis may also be accompanied by typical skin symptoms. It occurs mainly in childhood or in the fifth decade and affects women more often

Etiology
The cause is unknown. One possibility could be a autoimmune reaction against skeletal muscle, most likely triggered by an infectious agent. In 40-80% we find autoantibodies against the nuclear and cytoplasmic components of cells (Anti Mi-2, anti Jo-1). Thus, the occurrence of the disease is usually observable during viral diseases (coxsackies, echoviruses, paramyxoviruses, herpes viruses) - viruses trigger a defensive reaction that later degenerates into an autoimmune process. There is also an increased incidence of neoplasia.

Clinical picture
The disease begins with flu-like symptoms, arthralgias and Raynaud's phenomenon. In the acute phase, red-violet eyelid edema - heliotropic erythema - may occur. Gottron's papules are purple erythematous spots up to teleangiectasia found most often on the dorsum of the hand. Surface livid erythema also on the forehead, cheeks, neck and upper torso; photosensitivity is present; the dominant feature is progressive muscle weakness and pain - especially the proximal muscles of the limbs, torso and neck (typical difficulties when combing, placing objects in height); in severely ill patients, dysphagia is added - swallowing of swallowing muscles; dyspnoea in respiratory muscle damage.

 'Rare form:'   amyopathic dermatomyositis  - typical skin symptomatology without muscle damage

Complications
Pulmonary involvement (aspiration pneumonia, interstitial pulmonary fibrosis), joint involvement, more rarely the heart.

Diagnosis

 * 1) Symmetrical proximal muscle weakness
 * 2) Elevated creatine kinase (MM), aldolase or myoglobin
 * 3) EMG signs of myopathy
 * 4) Muscle biopsy with signs of inflammatory myopathy
 * 5) Typical skin manifestations

Differential diagnostics
Muscular dystrophies, myopathies - drug, toxic, endocrinological; toxoplasmosis, trichinosis

Therapy
Total corticoids, possibly with immunosuppressants (MTX)

Progress
In children, complete remission in half of the cases, chronic treatment is usually necessary in adults.

'' ' Malignant disease is present in 15-20%! ' ''