Mortality factors in idiopathic inflammatory myopathy: focusing on malignancy and interstitial lung disease.

Objectives: The objective of this study was to assess the incidence and common types of concomitant malignancies and to define predictive factors of death in Korean patients with idiopathic inflammatory myopathy (IIM).

Methods: From January 1989 to May 2011, 162 patients were diagnosed with IIM at a university hospital in Korea. The medical records were retrospectively reviewed. The clinical findings of the patients were compared for malignancy, and the prognostic factors predicting death were analyzed.

Results: Malignancies were found in 17 patients (10.5 %), all of whom had a significantly lower frequency of interstitial lung disease (ILD) and an older age at onset. The main causes of death were ILD and malignancy. Older age at diagnosis, presence of malignancy, rapidly progressive ILD and minimal creatinine phosphokinase (CPK) elevation were independent risk factors for death.

Conclusions: Malignancy was one of the most serious risk factor for death in our patients with IIM. Early discovery of malignancy is important, and an extensive investigation for common malignancies in each region should be done at diagnosis and for a minimum of 2 years thereafter. As minimally elevated CPK levels in ILD patients may be associated with fatal ILD, an early evaluation and a more aggressive treatment of ILD should be considered in these patients.