The frequency of peripheral blood eosinophilia and its clinical significance in patients with dermatomyositis.

In connective tissue diseases, eosinophil is thought to varying extents to be involved in the pathogenesis. Increased eosinophils in the skin tissues of patients with dermatomyositis (DM) have been reported, but there have been no investigations of blood eosinophilia in patients with DM. This study is the aim of determining the frequency of peripheral blood eosinophilia and elucidating its clinical significance. We retrospectively collected the clinical records of 48 patients (15 men and 35 women) who were diagnosed with classical DM (n = 34), ADM (n = 13), and JDM (n = 1), on the basis of the 2017 EULAR/ACR classification criteria for adult and juvenile idiopathic inflammatory myopathies. Eosinophil count ≥ 400/mm3 was observed in 14.6% (n = 7) of the patients, while 4.2% (n = 2) of patients had eosinophil counts >1,000/mm3. Regarding the clinical significance of peripheral blood eosinophilia in DM patients, in seven patients with increased blood eosinophil counts, the prevalence of Gottron's sign/papules, heliotrope rash, V-neck sign, shawl sign, pruritus, internal malignancy, and positive anti-TIF1-γ antibody were more frequent than in those without (85.7% , 85.7%, 71.4%, 71.4%, 85.7%, 42.9%, 28.6% vs. 92.7% p = 0.48, 61.0% p = 0.40, 36.6% p = 0.11, 39.0% p = 0.22, 36.6% p = 0.034, 19.5% p = 0.33, and 19.5% p = 0.63, respectively). Among them, pruritus was more common in patients with elevated eosinophil counts with statistical significance. The activity of eosinophilia and severity of skin eruptions also tended to be correlated. In summary, our study suggests that blood eosinophilia is correlated with the presence of pruritus, but not disease-associated autoantibodies or internal malignancy.