Complex t(1;15;17) in acute promyelocytic leukemia with duplication of RAR alpha and PML sequences

Area of Science:

• Hematology
• Cancer Genetics
• Molecular Biology

Background:

• Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia.
• APL is characterized by a specific chromosomal translocation, t(15;17), involving the retinoic acid receptor alpha (RAR alpha) and promyelocytic leukemia (PML) genes.
• Accurate genetic characterization is crucial for diagnosis and treatment of APL.

Observation:

• A 46-year-old male presented with flu-like symptoms and bleeding gums, leading to a diagnosis of APL with disseminated intravascular coagulation (DIC).
• Cytogenetic analysis revealed a complex rearrangement involving chromosome 17, with apparent deletions and an unknown source of additional material.
• Conventional banding techniques were insufficient to fully elucidate the complex chromosomal abnormality.

Findings:

• Fluorescence in situ hybridization (FISH) identified a derivative chromosome 17 (der(17)) with complex rearrangements, including duplication of RAR alpha and PML genes.
• The analysis confirmed the fusion of RAR alpha and PML sequences, consistent with the genetic hallmark of APL.
• Insertion of sequences from chromosomes 1 and 15 into the der(17) was also identified, highlighting a novel genetic mechanism.

Implications:

• This case demonstrates a rare and complex chromosomal aberration in APL, expanding the known spectrum of genetic alterations in the disease.
• The detailed molecular characterization provides insights into the formation of the derivative chromosome and the fusion of critical genes.
• Understanding such complex rearrangements may have implications for diagnostic refinement and potentially therapeutic strategies in APL.