Therapy-related Acute Promyelocytic Leukaemia: A Paediatric Case Report and Literature Review

Objective: To explore the clinical characteristics of therapy-related acute promyelocytic leukaemia (t-APL) after Langerhans cell histiocytosis (LCH) in a paediatric patient. Method: The clinical manifestations and laboratory findings of a rare paediatric case were analysed and relevant literatures were reviewed. Result: A paediatric patient with LCH who had completed the whole chemotherapy was admitted for proptosis and diagnosed as having relapsed LCH. However, the patient was finally diagnosed with t-APL after bone marrow immunophenotyping, fusion gene and a second bone marrow aspiration. Then, the patient was treated by the Chinese APL protocol. The patient responded well to the treatment and achieved complete remission after having completed induction chemotherapy. Conclusion: Paediatric doctors should take t-APL into consideration in their differential diagnosis when a LCH patients completed a whole session of chemotherapy. t-APL can be differentiated from relapsed LCH morphologically, immunologically, cytogenetically and molecular biologically.