PT  - JOURNAL ARTICLE
AU  - Khurram Abbass
AU  - Hollis Krug
TI  - Granulomatosis with polyangiitis in a patient with biopsy-proven IgG4-related pulmonary disease and coincident small cell lung cancer
AID  - 10.1136/bcr-2018-226280
DP  - 2019 Mar 01
TA  - BMJ Case Reports
PG  - e226280
VI  - 12
IP  - 3
4099  - http://casereports.bmj.com/content/12/3/e226280.short
4100  - http://casereports.bmj.com/content/12/3/e226280.full
SO  - BMJ Case Reports2019 Mar 01; 12
AB  - Granulomatosis with polyangiitis (GPA) was diagnosed in a patient with a 16-month history of IgG4-related lung disease that spontaneously became asymptomatic. Cytoplasmic antineutrophil cytoplasmic antibody (ANCA) was positive at the time of diagnosis of IgG4-related disease (IgG4-RD), but there was no vasculitis or kidney disease. Sixteen months later he developed rapidly progressive glomerulonephritis that responded to cyclophosphamide treatment. While undergoing treatment for GPA, he was found to have a lung mass identified as small cell lung cancer. This mass was present at the time of the IgG4-RD diagnosis. GPA can be confused with IgG4-RD histologically and they rarely coexist. ANCA antibodies are primarily IgG4 subclass. IgG4-RD has been associated with cancer and may improve prognosis. We speculate that this patient may have had small cell lung cancer that incited an IgG4 predominant immune response with coexistent ANCA antibodies that eventually resulted in GPA. Immunosuppressive treatment of GPA likely accelerated the progression of the lung cancer.