Low prevalence of malignancy in patients with idiopathic inflammatory myopathies in Jordan.

Objectives: To estimate the frequency of malignancy among patients with idiopathic inflammatory myopathies (IIM) in Jordan.
Methods: This was a retrospective review of case records of patients with IIM in Jordan.
Results: We identified 94 cases of IIM, (47 polymyositis (PM) and 47 dermatomyositis (DM)). Sixty-seven (71%) were females and 27 (29%) were males. The mean age at diagnosis was 39.7± 15.7 years (range 17-72), median 40 years and the mean follow-up was 5.05±4.03 years (0.2-19). Malignancy was diagnosed in only 4 patients (4.25%) with IIM. Among patients with DM, malignancy was found in three patients (6.4%).The age-standardised rate was 2.7% (95% confidence interval: 0. 6% to 7.1%). The standardised incidence ratio was 0.998. Diagnosis of associated malignancy was made close to the time of IIM diagnosis. Two male patients had nasopharyngeal carcinoma at the ages of 51 and 59 years, while the other two were female with breast and ovarian cancer at the ages of 40 and 45 years, respectively.
Conclusions: Malignancy in association with IIM was found to be low in our cohort in comparison to reports from other countries. The observed number of cancer cases in this group of patients is similar to the expected number of cases that would occur in general population of Jordan. This could be related to younger age of disease onset. The benefits of long-term screening for malignancy in our population are not clear.