POLIMIOSITIS

POLYMYOSITIS:

Idiopathic polymyositis is a diffuse inflammation of the skeletal muscles. An autoimmune process is suspected, in most cases.
Hypergammaglobulinemia, positive titers for serum antinuclear antibody (ANA), and elevations of circulating anti-muscle antibodies (also demonstrable by indirect immunohistology) have been found in many cases.
There is generalized weakness which worsens on exercise. These patients also have a stiff stilted gait, lameness and pain on muscle palpation.
Occasionally, generalized loss of skeletal muscle mass is evident.
Megaesophagus may be present with regurgitation and aspiration pneumonia.
The main features on examination are the stiff, stilted gait.
Neurologic examination (in a quiet room) is often within normal limits, except for possible muscle pain on palpation.
Other signs relate to the presence of aspiration pneumonia, including fever and listlessness.
During the acute phase, muscle enzymes will be elevated.
The diagnosis is supported by the findings of an abnormal needle EMG with normal nerve conduction velocities. There is occasionally a decremental response on repetitive nerve stimulation.
Muscle biopsy will confirm the diagnosis.

The treatment of polymyositis is with immunosuppressive doses of corticosteroids. Cases with aspiration pneumonia have a poor prognosis, since treatment with immunosuppressive drugs cannot be initiated. In those cases where corticosteroids are effective, monitoring the CPK may be useful in determining the course of therapy. If the CPK decline to normal for 1 month, the steroid medication can be stopped.
The prognosis is generally good if esophageal, pharyngeal and laryngeal muscles are not severely affected. The megaesophagus may resolve with therapy or be permanent.

Recently, (probably due to a more aggressive approach to muscle disease including biopsy and special staining procedures) many additional muscle diseases which present similarly to polymyositis have been uncovered.
Lipid-storage myopathy is one of these. These patients present with stiff, stilted painful gaits with tremendous pain on muscle palpation. Histopathology reveals increases in mitochondrial lipids on special (oil red O) stains. These patients may respond dramatically to coenzyme Q-10 and l-carnitine supplementation.

fuente: Universidad de Florida (USA)