Paediatric Acute Promyelocytic Leukaemia: A Rare Case Report

Abstract

Acute Myeloid Leukaemia (AML) is a malignant disorder of the bone marrow in which there is maturational arrest in blood cell progenitors, resulting in the failure of normal haematopoiesis. Acute Promyelocytic Leukaemia (APML) is a subtype of AML with a defined clinical course and a biology that is distinct from other forms of AML. Morphologically, the most common form of APML shows the presence of heavily granulated cells with folded and twisted nuclei in the bone marrow. Biologically, the cytogenetic changes define the syndrome, and molecular changes in the chromosomes play a critical role in leukaemogenesis. The occurrence of APML in the paediatric population is very rare, accounting for <5%. Here, a case is presented of a four-year-old child who with fever, one episode of non projectile vomiting, and two episodes of loose watery stools. Upon further investigation, the child had immature myeloid series cells in the peripheral blood smear, which on Bone Marrow Aspiration (BMA), flow cytometry, and Fluorescent In Situ Hybridisation (FISH) confirmed a case of APML. A major manifestation of this chimeric Promyelocytic Leukaemia (PML)-Retinoic Acid Receptor Alpha (RARA) protein is a maturation block at the promyelocyte stage of myeloid differentiation, leading to the accumulation of blasts and promyelocytes. Both Fluorescence In-Situ Hybridization (FISH) and Polymerase Chain Reaction (PCR) methods can detect the fusion gene, with PCR having the advantage of detecting the three major fusion transcripts and rare submicroscopic complex translocations. Additionally, quantitative PCR can be used to monitor minimal residual disease in APML following treatment. In this case, the patient survived her first episode of disease emergence, but during her relapse, she could not survive as she developed Disseminated Intravascular Coagulation (DIC), possibly due to chemotherapeutic agents. The patient might have developed differentiation syndrome, in which there is a large and rapid release of cytokines from leukaemic cells affected by chemotherapy agents. The challenge in treating such cases is to overcome differentiation syndrome and find a new therapy options.

Keywords

• differentiation
• flow cytometry
• platelets
• promyelocytes