Red cell fragmentation (schistocytosis) after bone marrow transplantation

Red cell fragmentation is often the earliest sign of thrombotic microangiopathy. Days +14, +28 and +42 blood films from 58 allograft and 32 autograft recipients were reviewed blind to determine the incidence and severity of schistocytosis (the number of fragmented red cells per 1000 red cells expressed as a percentage). Schistocytosis was graded as mild (< 1%), moderate (1-1.9%) or severe (≥ 2%). Schistocytes were seen in 99% of day 14 films (0.1-3.0%, median 0.4%), 97% of day 28 films (0.1-3.2%, median 0.4%), and 98% of day 42 films (0.1-4.3%, median 0.5%). Nine patients (10%) had severe fragmentation and 20 patients (22%) had moderate fragmentation at some time or the other. The difference in the extent of fragmentation between the days was not significant. Allogeneic BMT was associated with more extensive fragmentation than autologous transplantation on day 28 (P = 0.008) and day 42 (P = 0.02). Age, conditioning regimen and diagnosis had no influence. None of the patients followed-up for 6 months after transplant developed full-blown thrombotic microangiopathy. The occasional patient showing mild clinical and laboratory features of hemolysis responded well to adjustment of fluid balance and cyclosporine dose where applicable. Our data indicate that mild red cell fragmentation is a common morphologic finding after transplantation with no clinical significance in the absence of other clinical and laboratory findings suggestive of thrombotic microangiopathy, although patients with moderate or severe fragmentation should be monitored closely.