RESULTS: A total of 281 patients developed cGVHD between 2005 and 2013 and 51 of these patients had pleural or pericardial effusions. Of these, 39 were excluded either because effusions occurred before day 100 (not defined as cGVHD) or were due to other etiologies (CHF or infection). Overall, 12 patients met the criteria for cGVHD-associated serositis (incidence 4.2%). Male to female ratio was 1.4 and AML was the most common underlying malignancy (33%). All but one (91.6%) had previously established cGVHD with skin and GI being the most commonly involved organs. Median onset was 158 days after the initial diagnosis of cGVHD and 409 days after HSCT. We found a significant drop in serum albumin at presentation compared to one month prior (median 3.5 vs. 2.8g/dl, P value = 0.038). No significant change was found in the absolute monocyte count. Prior studies have not described analysis of pleural fluid in cGVHD-associated serositis. Six patients underwent thoracentesis (n=14, range=1-3), with 10 out of 14 (71%) being transudates. Two patients underwent pericardiocentesis, with 1 transudate. The mean lymphocyte count in pleural fluid was 55.7% (Range=7-94%). Complete drainage of pleural effusions appeared to be an effective treatment in 2 (14%) patients. Overall, treatment was challenging with patients typically unresponsive to augmentation in immunosuppressives.