If the clinical characteristics of both anti-MX1 autoantibody and anti-ARS autoantibody–positive patients with chronic fibrosing IIPs, including response to the recently developed drugs for IPF31, 32, could be clarified in more detail, we would be able to avoid the risk of surgical lung biopsy in a substantial number of non-IPF patients33; at present, biopsy is required for differential diagnosis of the patients belonging to the non-IPF category according to current ATS/ERS criteria. Here, MX1 is linked to idiopathic pulmonary fibrosis.