Dermatomyositis/polymyositis associated with malignancy: our experience with ten patients and review of relevant literature

Objective: To analyse the clinical and laboratory data of patients diagnosed with malignancy associated dermatomyositis/polymyositis (DM/PM) seen between January 2002 and February 2007. Methods: The demographic, clinical, treatment and follow-up data from the case records of all 10 patients diagnosed with malignancy-associated inflammatory muscle diseases (IMD) namely, DM/PM, were entered in a proforma and analysed. Results: In patient nos. 1-8, malignancy was diagnosed prior to the diagnosis of myositis; in patient no. 9, it was detected during screening and patient no. 10 developed breast cancer 5 years after PM diagnosis. All the patients had typical clinical and laboratory features of IMD, except two patients, who had amyopathic dermatomyositis with predominantly cutaneous features, creatine kinase levels less than two times the upper limit of normal and minimal muscle weakness. Breast cancer (6/10) and ovarian cancer (3/10) were the most commonly associated malignancies. All but one (patient no. 8) responded to treatment. Malignancy relapsed in four patients with concurrent relapse of myositis in three. These three patients died of the malignancy. One patient was lost to follow-up. The mean duration of follow-up in others was 21. months (range 12-60 months). Conclusion: DM is more commonly associated with malignancy. Carcinoma of the breast was the most commonly associated malignancy Myositis responded in most patients. Death was due to the underlying malignancy. In most cases, the two conditions occur within 1 year.