Serum ferritin correlates with activity of anti-MDA5 antibody-associated acute interstitial lung disease as a complication of dermatomyositis

Dermatomyositis (DM) is occasionally complicated by interstitial lung disease. Acute/subacute interstitial pneumonia (A/SIP) with DM is intractable and life threatening. Clinically amyopathic dermatomyositis (C-ADM) is also reported to be complicated with A/SIP, especially in those patients with anti-melanoma differentiation-associated gene 5 (MDA5) antibody. In the present cases, we indicate that serum ferritin level correlated with activity of A/SIP with DM. Two patients, a 65-year-old woman and a 30-year-old woman, were diagnosed with anti-MDA5 antibody-associated A/SIP with DM. Serum ferritin was high, 1600 and 770 mg/dl, respectively, on admission. Immunosuppressive therapy ameliorated A/SIP in both cases. Similarly, serum ferritin was also decreasing. However, A/SIP was recurrent and progressive, and serum ferritin was also increasing again in one case. In conclusion, serum ferritin correlates with disease activity of anti-MDA5 antibody-associated A/SIP with DM. Intensity of treatment may be decided according to serum ferritin level.