Lung Cancer Diagnosed More Than Five Years after the Development of Polymyositis/Dermatomyositis

Background. The patients with polymyositis (PM) and dermatomyositis (DM) often develop the malignancies in their clinical course. The incidence of cancer is estimated at about 15%. The risk of cancer is the highest within the first year of myositis diagnosis and drops substantially thereafter. The patients with lung cancer diagnosed more than 5 years after the onset of PM or DM are the minority. Methods and Patients. We surveyed the medical records of patients with lung cancer over the period from 1995 to 2011. Results. We found five patients who developed lung cancer more than 5 years after the diagnosis of PM/DM. Three patients were male, and two were female. The median age was 61.2 (±11.7). Histological types were diverse. The clinical stages ranged from IA to IV. Three patients had smoking histories. Four patients suffered from DM, and one suffered from PM. All patients received oral corticosteroid therapy. Two patients also received ciclosporin, and another two received azathioprine. Anti-Jo-1 antibody was positive in one patient. Four patients were complicated with interstitial pneumonia (IP). Conclusion. These lung cancers diagnosed more than 5 years after the onset of PM/DM were probably related to IP or smoking but might not be comorbid with PM/DM. 1. Background Idiopathic inflammatory myopathies are a group of chronic systemic autoimmune diseases that mainly affect the skeletal muscle. The common subtypes include adult dermatomyositis (DM), polymyositis (PM), and inclusion body myositis. In 1975, Bohan and Peter proposed the diagnostic criteria for DM and PM using clinical, laboratory, and pathological features which remain to be the gold standard for use in clinical studies (Table 1). These data were conducted in western population [1, 2]. On the other hand, Ungprasert et al. reviewed the characteristics of PM/DM in Asia [3]. They described that DM is more common, with the ratio of DM to PM being 1.36？:？1. Sixty-nine percent of them were females with mean age of 45.5 years. Extramuscular manifestations, including arthritis/arthralgia, dysphagia, and interstitial lung disease (IP), are found in one-third of the patients. They also clarified that the malignancy was found in 10% of patients. The link between PM and malignancy (gastric cancer) was first described in a case report by Sterz in 1916 [4]. While the most available evidence points to an association between DM and malignancy, the association with PM is much weaker [5, 6]. The incidence of cancer in patients with DM and PM is estimated at about 15% [7–10]. Of the cancers diagnosed before