PM may cause pain and tenderness over the muscles hence may be confused with Polymyalgia Rheumatica and Fibromyalgia.
Polymyositis is a systemic disease and hence has a range of physical symptoms. Some of the important symptoms associated with PM are:-
· Morning Stiffness
· Weight loss
Apart from these systems PM also tends to affect the pulmonary, GI, cardiac and systems and tends to co-present with certain malignancies and connective tissue disorder, in which case, it is referred to as overlap syndromes.
Pulmonary problems afflict approx 5-30% of patients suffering from PM (Especially associated with anti synthetase antibodies). The common manifestations of lung disease in PM are:-
· Intestial Lung Disease: It affects about 5-30% of patients suffering from PM and is strongly associated with the presence of anti Jo-1 antibodies. Patients present with dry cough, exertional Dyspnoea, and fever. Physical examination may reveal presence of Velcro crackles. At the base of the lung. Pulmonary Function Testing along with CO diffusion studies in conjunction with HRCT is the preferred modality for diagnosis.
· Patients may also develop exertional dyspnoea due to weakness of the thoracic muscles and diaphragm due to the myopathy. This is usually a poor prognostic sign.
· Involvement of the oropharyngeal muscles leads to repeated aspiration and aspiration pneumonia.
· Apart from these diseases bronchiolitis obliterans organizing pneumonia (BOOP), pulmonary capillaritis and Intestial pneumonitis have also been described as complications or associations of Polymyositis.
Cardiac manifestations are once again an adverse prognostic factor in PM. The common manifestations of cardiac muscle involvement include arrhythmias, cardiac failure, pulmonary hypertension, Myocarditis and pericarditis
Since PM affects the oropharyngeal musculature in about one third cases, GI symptoms are frequent and common cause of morbidity. The common GI symptoms include:-
· Swallowing difficulties
· Repeated aspiration
· Nasal regurgitation
· Abdominal Bloating
· Reflux oesophagitis (in overlap syndromes when associated with Scleroderma)
Polymyositis being an immune mediated disorder is associated with a myriad of rheumatic and connective tissue disorder. This has spawned the term Overlap Syndromes. Overlap syndromes refers to a distinct subset of disorders where PM is associated with other connective tissue disorders, namely, Systemic Lupus, Scleroderma, Mixed Connective tissue disease, and Sjogren Syndrome.
The association between scleroderma and Pm is particularly striking as up to 25% of Scleroderma patients have Myositis and these patients are usually positive for anti PM-Scl (Anti PM-1) antibody. Japanese patients have an association with anti-Ku antibody.