[Langerhans cell histiocytosis and myelomonocytic leukemia: a non-fortuitous association]. / Histiocytose langerhansienne et leucémie de la lignée myélomonocytaire: une association non fortuite.

BACKGROUND: Langerhans cell histiocytosis is an uncommon clonal disorder. Its reactional or genetic nature is debated. CASE REPORT: Three patients aged 71, 75 and 73 years with Langerhans cell histiocytosis also developed myelomoncytic leukemia (AML4, AML5, and chronic myelomonocytic leukemia). In two cases, there was no prior treatment which could potentially induce leukemia. In the third case, AML4 occurred shortly (10 months) after initiation of a vinblastin treatment. DISCUSSION: This pathogenic association suggests a common origin for these two conditions, corresponding to an anomalous pluripotent stem cell line. These cases provide further evidence favoring the hypothesis of a genetic origin rather than a reactional origin for Langerhans cell histiocytosis.