Long-term follow-up of 76 Iranian patients with idiopathic inflammatory myopathies

This study aimed to follow up patients with polymyositis (PM) and/or dermatomyositis (DM) to determine survival rate, pattern of disease, response to treatment, malignancy incidence and poor prognostic factors (PPFs).

A total of 76 patients with PM (n = 47) and/or DM (n = 29) based on Bohan and Peter diagnostic criteria referred to the Imam-Reza Hospital were followed up from 2004 to 2016. The follow-up period was considered from diagnosis to patient's death or last visit. All patients underwent physical examinations and data including age, sex, disease duration, disease subtype, pattern of disease, PPFs and malignancy incidence were collected.

Mean age at diagnosis was 45.49 ± 10.88 years and women were predominant (84.2%). Course of disease in the majority of patients (52.6%) was polyphasic, followed by monophasic (31.6%) and chronic-progressive (5.3%). The 1-, 5- and 10-year survival rates were 96%, 93% and 92%, respectively. Delay in treatment and dysphagia were common PPFs in the present study. The majority of patients responded to treatment (88.2%) and there were significant differences in cancer and dysphagia between responders and non-responders to treatment (P < 0.05). The most common cause of death was cancer in four of eight deaths. There was significant difference in survival rates between patients with and without pulmonary involvement (P = 0.001). Moreover, the survival rates were significantly lower in patients with malignancy (P = 0.001).

Presence of dysphagia and cancer were associated with poor response to treatment. Pulmonary involvement and cancer incidence significantly affect survival rate. Furthermore, since cancer is the most common cause of death, so this study emphasizes the importance of careful cancer screening in these patients.