Juvenile myelomonocytic leukemia presenting with features of neonatal hemophagocytic lymphohistiocytosis and cutaneous juvenile xanthogranulomata and successfully treated with allogeneic hemopoietic stem cell transplant.

Juvenile xanthogranuloma (JXG) is rarely associated with either hemophagocytic lymphohistiocytosis (HLH) or juvenile myelomonocytic leukemia (JMML) and when in association with the latter there is usually neurofibromatosis type 1. We report a child who presented with JXG and HLH during the neonatal period and who subsequently developed JMML during early infancy in whom there is no evidence of neurofibromatosis type 1. The patient was refractory to standard HLH therapy but he is well and is now 42 months after mismatched unrelated donor hemopoietic stem cell transplant without evidence of HLH or JMML. His JXG lesions show involution, in keeping with the expected natural history of this disorder.