PT - JOURNAL ARTICLE AU - Camilo Vargas AU - Carolina Velásquez AU - Edgardo Mancilla AU - Joaquín Aracena TI - IgG4-related lung disease as a differential diagnosis of a lymphoproliferative disease: atypical presentation of an atypical disease AID - 10.1136/bcr-2021-247295 DP - 2022 Jan 01 TA - BMJ Case Reports PG - e247295 VI - 15 IP - 1 4099 - http://casereports.bmj.com/content/15/1/e247295.short 4100 - http://casereports.bmj.com/content/15/1/e247295.full SO - BMJ Case Reports2022 Jan 01; 15 AB - IgG4-related disease (IgG4-RD) is an immunomodulated inflammatory disease that usually affects the pancreas and parotid glands. Although lung involvement is rare, it has been recently reported and could mimic various other diagnoses. We present a case of IgG4-RD whose symptoms and images raised the suspicion of a malignant lymphoproliferative lung neoplasm. It is imperative to differentiate both diseases, since their treatment and prognosis vary.