An Acute Promyelocytic Leukemia Resistant to All-Trans Retinoic Acid: A Case Report of the <i>ZBTB16::RARa</i> Variant and Review of the Literature

Abstract

<b><i>Introduction:</i></b> Acute promyelocytic leukemia (APL) is characterized by the <i>PML::RARa</i> gene fusion and treatment consists of all-trans retinoic acid (ATRA). Rarely, genetic APL variants have been described which are insensitive to ATRA treatment and are therefore associated with a worse prognosis. Rapid identification of the APL variant is essential to start the correct treatment. <b><i>Case Presentation:</i></b> Here, we present a case of a 66-year-old male patient with weight loss and arthralgia. Laboratory results showed an anemia and mild leukocytosis with predominantly monocytes. Bone marrow investigation unexpectedly revealed a t(11;17)(q23;q21). This raised suspicion of an ATRA-resistant APL. By demonstrating the <i>ZBTB16::RARa</i> gene fusion, the diagnosis was confirmed. <b><i>Conclusion:</i></b> This case study emphasizes the importance of integrated diagnostics and provides guidance to recognize the <i>ZBTB16::RARa</i> APL, which is the most prevalent ATRA-resistant APL. Furthermore, an overview of other genetic APL variants is presented and how to treat these uncommon diseases in clinical practice.