Acquired factor XIII deficiency and its unprecedented association with multiple myeloma: case report and literature review.

This case involves a 58-year-old patient, with no personal or family history of bleeding, diagnosed with stage III-A IgG Kappa multiple myeloma in 2016 and underwent autografting in 2017. In March 2022, he suffered a myeloma relapse. In October 2022, the patient presented with a large spontaneous compressive hematoma in the left shoulder and hemithorax, requiring two surgical procedures. The platelet count and hemostasis parameters were within normal range. Further diagnostic testing revealed acquired factor XIII deficiency and acquired thrombopathy. Diagnostic challenges arose from the absence of specific assays for the B subunit of Factor XIII. Treatment involved transfusions and corticosteroids, but efficacity was limited. The patient's response to chemotherapy raised questions about the involvement of the monoclonal component. Subsequent follow-ups showed factor XIII levels fluctuating, even without symptoms. The patient was deemed ineligible for autograft due to a significant risk of hemorrhage.