Occurrence of acute nonlymphoblastic leukemia in two girls after treatment of recurrent, disseminated Langerhans cell histiocytosis.

The occurrence of Langerhans cell histiocytosis (LCH) and acute leukemia in one individual has rarely been observed. Despite few exceptions, two distinct patterns of association appear evident: acute lymphoblastic leukemia preceding LCH and LCH preceding acute nonlymphoblastic leukemia (ANLL). The latency of ANLL after the diagnosis of LCH is suggestive of a therapy-related process. This report describes two new cases in whom ANLL was diagnosed 7 years 8 months and 5 years 8 months after the start of initial treatment of disseminated recurrent LCH. Morphology showed blasts from FAB-type M4/M5 in the first patient, who died due to progression of leukemia. The second patient showed myelodysplastic syndrome (refractory anemia with excess of blasts in transformation; RAEB-t) and is now in remission from leukemia 3 years 11 months after allogeneic bone marrow transplantation. The review of a total of 26 patients with ANLL after LCH suggests that the disease has a poor prognosis and allogeneic BMT seems to be the treatment of choice.