Rationale: Juvenile myelomonocytic leukemia (JMML) is a rare hematopoietic disorder, which is more rarely accompanied by monosomy 5 or deletion of the long arm of chromosome 5q (-5/5q-) or monosomy 5 (5q-/-5), and hemophagocytic lymphohistiocytosis (HLH) is a rare, uncontrolled hyperinflammation condition, which is more rarely secondary to JMML. Up to now, only a few cases of JMML with -5/5q- and HLH secondary to JMML were described. Here we described an extremely rare case of HLH second to JMML with 5q-.
Patient concerns: The patient had multiple cafe-au-lait-spots at birth and was found that NF1 gene mutation was positive. At his 6 years old, he developed hepatosplenomegaly, anemia, thrombocytopenia, monocyte count 4.12×109/L in peripheral blood, 13% blasts in peripheral blood, and 11% blasts in bone marrow, without BCR/ABL rearrangement, combining with positive NF1 gene mutation, he was diagnosed as JMML. In the bone marrow, there was chromosomal abnormalities with -5/5q-. In the treatment, HLH occurred.
Diagnoses: The patient was diagnosed as secondary HLH to JMML.
Interventions: The patient received the chemotherapy treatment of the improved diffuse alveolar hemorrhage protocol, and meanwhile, he prepared for hematopoietic stem cell transplantation. Then on the basis of anti-infection, symptomatic and supportive therapy, he was commenced the treatment according to the HLH-2004 protocol.
Outcomes: He had a partial response, manifesting that his fever resolved, but the blood coagulation function did not improve, and the severe thrombocytopenia remained. Then, the parents refused the continual treatment, and the child died of intracranial hemorrhage 3 months after the diagnosis of JMML.
Lessons: JMML and HLH were relatively easy to diagnose based on clinical and laboratory results. Due to the low incidence of JMML with -5/5q- and HLH secondary to JMML, no clinical practice guidelines for the treatment of the disease have been established yet. The clinical data of a case of HLH secondary to JMML with 5q- were analyzed, and relevant studies were studied.