COPYRIGHT © by Michaelidou Maria
Dr. Maria Michailidou
Inflammatory myopathies are rare diseases. Estimates of incidence range from 0.5 to 8.4 cases per million. The incidence does appear to be increasing, although this may simply reflect increased awareness and more accurate diagnosing. lists the clinical classification of the idiopathic inflammatory myopathies.
These diseases are seen in all age groups, but overall, the age at onset has a bimodal distribution with peaks observed between ages 10 and 15 years in children and between 45 and 60 years in adults. However, the mean ages for specific groups differ. Both myositis associated with malignancy and inclusion body myositis are more common after age 50 years. The age at onset for myositis occurring with another collagen vascular disease is similar to that for the associated condition. Women are twice as commonly affected as men, with the exception of inclusion body myositis, which affects men more often.
Symptoms and Signs of polymyositis
The clinical features of polymyositis in the adult are representative of all the inflammatory myopathies. Typically, polymyositis begins insidiously over 3–6 months with no identifiable precipitating event. Pelvic and shoulder girdle musculature are most affected, but weakness of neck muscles, particularly the flexors, is also common. Ocular and facial muscles are virtually never involved. Dysphagia may develop secondary to esophageal dysfunction or cricopharyngeal obstruction. Pharyngeal muscle weakness may cause dysphonia and difficulty swallowing. Myalgias and arthralgias are not uncommon, but severe muscle tenderness and frank synovitis are unusual. Raynaud phenomenon is sometimes present, and periorbital edema may be noted.
Pulmonary and cardiac manifestations may precede the onset of muscle weakness or
develop at any time during the course of disease. Velcro-
The clinical features of dermatomyositis include all those described for polymyositis
plus a variety of cutaneous manifestations. Skin involvement varies widely from patient
to patient. Rashes can antedate the onset of muscle weakness or follow its development
by more than a year. Furthermore, the characteristics of the rash may change over
time. Two cutaneous manifestations are considered pathognomonic. These include Gottron
papules (symmetric lacy pink or violaceous raised areas typically found on the dorsal
aspect of interphalangeal joints, elbows, patellae, and medial malleoli) and heliotrope
(violaceous) discoloration of the eyelids. The latter is often with associated periorbital
edema. Other characteristic cutaneous findings include macular erythema of the posterior
shoulders and neck (shawl sign), anterior neck and upper chest (V-
The inflammatory myopathy that affects children tends to have a highly characteristic pattern, although a disease similar to adult polymyositis does occur. In juvenile dermatomyositis, the skin lesions and weakness are almost always coincidental, but the severity and progression of each varies greatly from patient to patient. In some patients, remission is complete with little or no therapy. The juvenile variant differs from the adult form because of the coexistence of vasculitis, ectopic calcification, and lipodystrophy. Unfortunately, in dermatomyositis accompanied by vasculitis, progression may be devastating despite therapy. Gastrointestinal ulcerations resulting from vasculitis can cause hemorrhage or perforation of a viscus. Ectopic calcifications may occur in the subcutaneous tissues or in the muscles.
Some patients with biopsy-
Muscle weakness is a common finding in patients with collagen vascular diseases. The features of idiopathic inflammatory myopathy may dominate the clinical picture in some patients with scleroderma, systemic lupus erythematosus, mixed connective tissue disease, and Sjögren's syndrome, but the classic picture of polymyositis is less common in rheumatoid arthritis, Wegener granulomatosis, polyarteritis nodosa, and adult Still disease. Weakness in these latter conditions is more commonly the result of vasculitis.
Muscle weakness associated with an underlying malignancy develops in a subset of
patients with inflammatory myopathies. The true incidence of this relationship is
not clear. Although malignancy may precede, or develop after, the onset of muscle
weakness, usually the two are diagnosed within a 1-
Inclusion body myositis mainly affects older persons. The symptoms begin most insidiously and progress slowly. Symptoms are often present for 5–8 years before the diagnosis is made. The clinical picture in some patients is identical to that of typical polymyositis. In others, however, focal, distal, or asymmetric weakness is present. Dysphagia is not infrequent in this disease. As the muscle weakness becomes severe, it can be accompanied by atrophy and diminished deep tendon reflexes. In some patients, inclusion body myositis follows a slow, steadily progressing course. In others, the weakness seems to plateau, leaving the person with fixed weakness and atrophy of the involved musculature.
Laboratory Findings of polymyositis
An abnormal kinase (CK) level is possibly the most sensitive indicator of skeletal muscle damage. The serum level of this enzyme is elevated at some time during the course of an inflammatory myopathy and, in most instances, the serum CK level reasonably correlates with disease activity. Normal levels of CK may be found very early in the course of polymyosits or dermatomyositis, in advanced cases with significant muscle atrophy, or in myositis associated with a malignancy. CK levels are often only minimally elevated or can be normal in inclusion body myositis. Other enzymes derived from diseased skeletal muscle include aldolase, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH). Accordingly, these enzymes may also be elevated in the course of the disease.
Tests of acute phase reactants, the erythrocyte sedimentation rate (ESR) and C-
Antinuclear antibodies (ANAs) may be found in the serum of over 50% of patients with
inflammatory muscle disease. The presence of a high-
Certain autoantibodies are found almost exclusively in patients with idiopathic inflammatory
myopathies and, therefore, are termed myositis-