Polymyositis and dermatomyositis

What are they ?

Within the defense mechanisms of the immune system have some types of lymphocytes, B lymphocytes, which are transformed into plasma cells, the cells that generate antibodies that detect compounds parts of the body outside agents – antigens – and to identify potential threats and attack them, as they do with bacteria and viruses.

In normal plasma cells only recognize as foreign elements foreign to the body and also have mechanisms to recognize cells and the body’s own proteins. But for various reasons when there is a disturbance of this ability to recognize themselves as organic components, plasma cells may generate antibodies against the body itself and cause various changes depending on the type of tissue, cell or protein that attack. When this happens we speak of an autoimmune disease.

Muscles are no strangers to these potential changes and when the body creates antibodies that attack the muscle fibers, which is the death of muscle cells, inflammatory myopathies discussing, among which the most common are polymyositis and dermatomyositis.

How do you produce ?

Inflammatory myopathies in some cases have a genetic component to be determined. It has also been postulated the importance of certain viral infections which may alter the previous recognition own muscle tissue as by antibodies.

Inflammatory myopathies within a specific entities include, namely:

• polymyositis
• juvenile dermatomyositis
• adult dermatomyositis
• Inclusion body myositis
• neoplasms associated myositis
• vasculitis associated myositis
• myositis associated with collagen disease

Polymyositis usually occurs in young people, especially women, like dermatomyositis in adults and children.The inclusion body myositis often affects young males more.

In inflammatory myopathies were detected cellular immune mechanisms involved, ie intervention occurs defense cells as T8 lymphocytes, macrophages and polymorphonuclear cells and antibody being characteristic of these diseases Mi anti- 2, anti-Jo-1 (especially in polymyositis) and SRP antibodies, the presence of which tends to reflect a severe cardiac muscle involvement.

Symptoms

The main symptoms derived inflammatory myopathies, muscular, chronic inflammation that occurs in the muscles and that leads to necrosis of the muscle tissue.

Polymyositis represents approximately 35% of the inflammatory myopathies and muscular involvement characterized by symmetric proximal start introducing over weeks or months. Patients complain of muscle weakness that prevents them from doing everyday activities, and only 20% of patients report muscle pain.Often associated with dysphagia can lead to aspiration episodes, with subsequent respiratory infections. In the lungs so you can give intercostal muscle involvement, which makes breathing difficult, and interstitial pneumonitis. The heart can also be affected with miocaridopatías, arrhythmias or pericarditis. Rarely affects the eye muscles.

Dermatomyositis represents a third of the patients with inflammatory myopathies. It is characterized by muscle involvement equal to but polymyositis associated with cutaneous manifestations. In areas exposed to the sun appears erythema is classically called heliotrope and characteristically is given around the eyes. Over bony prominences such as the knuckles, erythematous spots appear that are called Gottron papules. The hands usually have a thick skin and cracked. These patients can present itself with the effort muscle pain and muscle edema and eventually atrophy. Calcifications occur frequently in affected muscles. The organic manifestations of dermatomyositis are similar to those of polymyositis.

In inclusion body myositis the onset of symptoms is insidious, hard years, and muscle involvement, unlike the previous ones, is both proximal and distal.

The most common malignancies associated with inflammatory myopathies are the lung, ovary, breast, stomach and myeloproliferative syndromes. Myopathies associated tumors represent less than 10% of the total.

Inflammatory myopathies are associated collagenopathies one fifth of the total and the diseases that most often they are associated with systemic sclerosis, rheumatoid arthritis, lupus erythematosus and mixed connective tissue disease.