Pulmonary cytolytic thrombi: a newly recognized complication of stem cell transplantation

Over the past 5 years we have recognized a new pulmonary complication of he matopoietic stem cell transplantation (HSCT) associated with fever and pulm onary nodules termed 'pulmonary cytolytic thrombi' (PCT), Retrospective ana lysis of medical and radiographic records and pathologic material from 13 H SCT recipients with PCT and a review of the Blood and Marrow Transplant Dat abase for all patients with radiographic evidence of pulmonary nodules or w ho underwent open-lung biopsy from 1 January 1993 to 31 December 1998 (n = 1228) were performed. The median age of patients with PCT was 11.9 years (r ange, 1.3-29.7 years). All patients developed fever at a median of 72 days (range, 8-343 days) post transplant, followed by pulmonary nodules on chest CT. Eleven patients were receiving therapy for active GVHD (acute, grades I-IV (n = 10); extensive chronic (n = 1)). Biopsy of the pulmonary nodules revealed a unique pattern of necrotic, basophilic thromboemboli with amorph ous material suggestive of cellular breakdown products. This was descriptiv ely labeled 'pulmonary cytolytic thrombi', Immunohistochemical staining rev ealed entrapped leukocytes and disrupted endothelium, but was negative for histiocytes, Cultures and immunohistochemical stains were negative for infe ctious agents. Empiric therapy included systemic corticosteroids (n = 9) an d amphotericin (n = 7), Nine patients survive with resolution of PCT at a m edian follow-up of 1.5 years.