An association exists among neurofibromatosis 1 (NF1), juvenile xanthogranulomas (JXGs), and juvenile myelomonocytic leukemia (JMML). The authors describe a patient with the triple association of JXG, NF1, and JMML initially presenting with features of hemophagocytic lymphohistiocytosis (HLH). An 18-month old boy had multiple cutaneous and gastrointestinal JXG and NF1. At 3 years of age he developed anemia, thrombocytopenia, and hepatosplenomegaly. A bone marrow biopsy revealed features of HLH. Despite chemotherapy, he went on to develop JMML, which proved fatal.