IgG4 related disease is a recently recognized chronic fibrotic, inflammatory condition, caused by infiltrating IgG4 positive plasma cells that can cause tumor like disease in almost any organ in the body. Typical histopathology is lymphoplasmocytic infiltration of IgG4 positive cells, storiform fibrosis and obliterative phlebitis. Glucocorticoids alone or in combination with B-cell depletion with rituximab causes often good, lasting response. We present here a lady with recurrent lung infiltration that simulated pneumonia and later tumor of the lung. She was also earlier diagnosed with lump in the breast that was found to contain similar IgG4 positive plasma cells that was also demonstrated in the lung biopsy. She responded very well to rituximab given on 2 occasions. Three years after this treatment she is in total remission.

Figure 1.

Computerized tomography (CT) scan of the lungs taken in January 2013 shows extensive tumor like infiltration in the middle of the right lung.

Figure 2.

IgG 20x immunological staining for IgG4, that stains large number of plasma cells in the lung tissue.

Figure 3.

Computerized tomography scan of the lungs taken in February 2015 almost two years after the rituximab treatment, shows normal CT scan