History
Symptoms of polymyositis gradually develop over a period of 3-6 months. Diagnosis is usually delayed, because, unlike in dermatomyositis, no associated rash occurs before the onset of muscle disease. Family history and medication history are important in excluding other causes of myopathy.
The history of patients with polymyositis or dermatomyositis typically includes the following:
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Symmetrical, proximal muscle weakness with insidious onset
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Pain is not a predominant symptom (Myalgias occur in fewer than 30% of patients.)
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Dysphagia (30%) and aspiration, if pharyngeal and esophageal muscles are involved
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Arthralgias may be associated
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Difficulty kneeling, climbing or descending stairs, stepping onto a curb, raising arms, lifting objects, combing hair, and arising from a seated position
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Weak neck extensors cause difficulty holding the head up
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Involvement of pelvic girdle usually greater than upper body weakness
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Cardiac involvement may cause symptoms of pericarditis or cardiomyopathy
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Characteristic rash on face, trunk, and hands seen in dermatomyositis only
Muscular symptoms
Patients with polymyositis usually present with symmetrical, proximal muscle weakness in the upper and lower extremities. Weakness of neck flexors also occurs. Patients with polymyositis may occasionally report muscle pain and tenderness, which may be confused with symptoms of polymyalgia rheumatica. The disease may exist for several months before the patient seeks medical advice, and all of the muscles of the thighs, trunk, shoulders, hips, and upper arms are usually involved. Muscle weakness may fluctuate on different days and at different times.
Fine motor movements that depend on the strength of distal muscles, such as buttoning a shirt, sewing, knitting, or writing, are affected only late in the disease.
Dysphagia secondary to oropharyngeal and esophageal involvement occurs in about one third of patients with polymyositis and is a poor prognostic sign. Dysphonia is also a poor prognostic sign but is much less common.
Ocular muscles are never involved in generalized polymyositis. However, isolated orbital myositis, an inflammatory disorder involving the extraocular muscles, is well described. Facial and bulbar muscle weakness is extremely rare in individuals with polymyositis.
A family history of neuromuscular disease, endocrinopathy, or exposure to myotoxic drugs or toxins is absent.
Constitutional symptoms and signs
Polymyositis is a systemic disease. Symptoms and signs may include the following:
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Morning stiffness
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Fatigue
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Anorexia
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Fever (associated with antisynthetase antibodies such as anti–Jo-1)
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Weight loss
Pulmonary manifestations
Pharyngeal and esophageal weakness may lead to aspiration pneumonia. Patients with polymyositis may experience exertional dyspnea secondary to weakness of chest wall muscles and diaphragmatic muscles. Patients receiving immunosuppressants are at an increased risk of infection.
Interstitial lung disease occurs in 5-30% of patients with idiopathic inflammatory myopathy (associated with antisynthetase antibodies, especially anti–Jo-1). Patients may be asymptomatic or present with exertional dyspnea, cough, and fever. [20]
Interstitial pneumonitis, bronchiolitis obliterans organizing pneumonia, and pulmonary capillaritis have been described in conjunction with polymyositis.
Cardiac manifestations
Cardiac involvement is unusual and, if present, portends a bad prognosis. Rhythm disturbances, conduction defects, congestive heart failure, pericarditis, pulmonary hypertension, and myocarditis can occur.
Joint involvement
Patients can present with arthralgias or arthritis. Arthritis is usually symmetrical and involves the knees, wrists, and hands (associated with antisynthetase antibodies). A severe, deforming arthropathy without erosions has been reported; erosive changes are very rare.
Overlap syndromes
Polymyositis has been associated with other connective-tissue diseases, including the following:
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Systemic lupus erythematosus
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Rheumatoid arthritis
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Mixed connective-tissue disease
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Sjögren syndrome
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Scleroderma
About 25% of patients with scleroderma have myositis; this phenomenon has been associated with anti-PM/Scl (anti–PM-1) antibody. In Japan, anti-Ku antibody has been described with this condition.
Gastrointestinal manifestations
Symptoms may include the following:
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Dysphagia
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Odynophagia
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Nasal regurgitation
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Reflux esophagitis
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Abdominal bloating
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Constipation
Renal manifestations
Intrinsic kidney disease is rare in patients with polymyositis. Occasionally, severe rhabdomyolysis with myoglobinuria can result in acute tubular necrosis.
Cutaneous manifestations
Unlike in dermatomyositis, rash is absent in polymyositis. However, "mechanic's hands" (associated with antisynthetase antibodies), ie, hyperkeratotic eruptions over the finger pads and lateral aspects of the fingers can be seen.
Raynaud phenomenon has been described in patients with antisynthetase antibodies. Rarely, periorbital edema may occur (best described in dermatomyositis). Calcinosis occurs in approximately 5% of patients with polymyositis (in association with scleroderma-like illness). Telangiectasias are uncommon.
Amyopathic dermatomyositis is a condition in which patients have cutaneous findings of dermatomyositis without muscle weakness.
Inclusion body myositis
This condition is a slowly progressive, idiopathic, inflammatory myopathy that mostly affects men older than age 50 years. Muscle involvement predominantly includes proximal muscles but may also include distal muscles (50%), and involvement may be asymmetrical. Dysphagia occurs in most patients (60%).
Physical Examination
Muscle weakness in polymyositis is symmetric and proximal. It is not painful, although a minority of patients report aches or cramps. On occasion, the muscle may be sore to palpation and may have a nodular and grainy feel.
Sensory examination findings are normal. Ocular and facial muscles remain normal even in advanced, untreated cases. However, ocular involvement can result in significant retinal inflammation associated with hemorrhage with possible detachment resulting in vision loss. [21]
The pharyngeal and neck flexor muscles are often involved, causing dysphagia and difficulty in holding up the head. When the patient is first seen, many of the muscles of the trunk, shoulders, hips, upper arms, and thighs are usually involved. In restricted forms of the disease, only the neck or paraspinal muscles (camptocormia) are affected. [22]
In advanced cases and rarely in acute cases, respiratory muscles are affected. Severe weakness is almost always associated with muscular wasting. Dysphonia with nasal speech may be noted. Lung examination findings may include evidence of interstitial lung disease, such as dry inspiratory crackles ("Velcro") in the lung bases.
The tendon reflexes are preserved, but they may be absent in severely weakened or atrophied muscles.
Primary cardiac abnormalities due to myocarditis may be present in a few patients. These abnormalities mainly manifest as atrioventricular conduction defects, tachyarrhythmias, low ejection fraction, dilated cardiomyopathy, or congestive heart failure.
General systemic disturbances, such as fever, malaise, weight loss, arthralgia, and Raynaud phenomenon, may occur when polymyositis is associated with another connective-tissue disorder.
Inclusion body myositis
Inclusion body myositis manifests as severe, proximal muscle weakness with atrophy, often with distal muscle weakness. The weakness may be asymmetrical. Deep tendon reflexes may be impaired or absent if weakness is severe.
Complications
Complications include the following:
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Polymyositis. MRI of thighs showing increased signal in the quadriceps muscles bilaterally consistent with inflammatory myositis.
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Polymyositis. Histopathology slide shows endomysial mononuclear inflammatory infiltrate and muscle fiber necrosis.
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Polymyositis. Close view of muscle biopsy, showing chronic inflammatory infiltrate consisting of T lymphocytes, especially CD8+ T lymphocytes.
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Polymyositis. Hematoxylin and eosin frozen section shows polymyositis. Endomysial chronic inflammation is present among intact myofibers, which are remarkable only for increased variability of fiber size. Image courtesy of Roberta J. Seidman, MD.
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Polymyositis. Hematoxylin and eosin paraffin section shows polymyositis. Patient had dense endomysial inflammation that contains an abundance of plasma cells, which can be observed in patients with chronic polymyositis. Two necrotic myofibers, characterized by dense eosinophilic staining, are observed. Focal fatty infiltration of the muscle is present in the lower left quadrant of the photomicrograph. Image courtesy of Roberta J. Seidman, MD.
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Polymyositis. Hematoxylin and eosin paraffin section shows polymyositis. Photomicrograph illustrates attack on a nonnecrotic myofiber by autoaggressive T lymphocytes. On the left, the central myofiber is intact. On the right, it is obliterated by a segmental inflammatory attack. If immunohistochemistry were performed, expected findings would include an admixture of CD8 T lymphocytes and macrophages in the inflammatory process. Image courtesy of Roberta J. Seidman, MD.
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Polymyositis. Hematoxylin and eosin paraffin shows dermatomyositis. In dermatomyositis, inflammation is characteristically perivascular and perimysial. Vessel oriented approximately vertically in the center has a mild perivascular chronic inflammatory infiltrate. The endothelium is plump. The wall is not necrotic. A few lymphocytes in the wall of the vessel are probably in transit from the lumen to the external aspect of the vessel. Some observers may interpret this finding as vasculitis, but it is certainly neither necrotizing vasculitis nor arteritis. Image courtesy of Roberta J. Seidman, MD.
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Polymyositis. Hematoxylin and eosin paraffin section shows polymyositis. Longitudinal section shows a dense, chronic, endomysial inflammatory infiltrate. Image courtesy of Roberta J. Seidman, MD.
