Letterer-Siwe disease associated with chronic myelomyonocytic leukemia: a fortuitous association?

Langerhans cell histiocytosis (LCH) and malignancy occurring in the same individual is unusual and has generally been the subject of isolated case reports. LCH is a rare condition in adults. Its cause is uncertain but, with the recent demonstration of clonality and its association with malignant disease, there has been a renewal of interest. We report a singular case of Letterer-Siwe disease associated with a chronic myelomonocytic leukemia developing in an elderly woman. The simultaneous occurrence of both malignant disorders supports the hypothesis of a common genetic origin.