To report a case of a patient diagnosed with CMML with recurrent subdural hematomas and platelet dysfunction.

The case report was based on data recorded in the electronic medical record and literature review.

A 62-year-old female diagnosed with CMML in February 2022 during investigation of persistent monocytosis associated with anemia and thrombocytopenia. Hemoglobin: 8.9 g/dL; White blood cell count: 11,860/mm3 (69/0/0/9/20); Platelets: 45,000/mm3. BCR-ABL and JAK2 tests were negative. Bone marrow examination revealed erythroid and granulocytic hypercellularity with dysplastic changes. Megakaryocytes were hypolobulated. The patient presented with a left subdural hematoma following a mild traumatic brain injury in October 2022, requiring neurosurgical intervention. At that time, coagulation profile and platelet levels were normal. In December 2022, she experienced headaches again, with a subdural hematoma on the right side without any history of local trauma. The hematoma was drained once more, and laboratory tests continued to show normal platelet levels and coagulation profile. After discharge, the patient presented with neurological symptoms in January 2023, and a new right-sided subdural hematoma required two additional surgical interventions. Structural abnormalities were not detected on imaging exams. Given the recurrent episodes of severe intracranial hemorrhage with a risk of herniation, the hypothesis of platelet dysfunction associated with CMML was considered, and platelet transfusion was performed. After this intervention, there were no further bleeding episodes, and subsequent platelet aggregation testing confirmed hypoaggregation with collagen, ristocetin at a concentration of 1.2 mg/mL, adrenaline, and arachidonic acid. In outpatient follow-up, the patient showed an increase in white blood cell count and anemia with thrombocytopenia, and she received the AZAVIT-ABCDEF protocol (azacitidine, erythropoietin, filgrastim associated with high doses of vitamin B1, C, and D3) after signing the informed consent. There was no recurrence of central nervous system bleeding, and the leukocytosis and monocytosis were controlled.

CMML is a condition characterized by persistent monocytosis associated with dysplastic morphology in the bone marrow and can exhibit features of either myelodysplastic neoplasms or chronic myeloproliferative diseases. It is associated with various mutations, including the TET2 gene mutation, which occurs in up to 60% of patients and appears to lead to mild platelet dysfunction. Platelet transfusions stopped the intracranial hemorrhage, and high doses of vitamin C possibly restored the function of the TET2 gene.

Advanced in molecular studies may further elucidate the heterogeneity of these myeloid disorders with uncertain clinical behavior and assist in therapeutic decision-making. The patient in this case was diagnosed with CMML and presented with recurrent subdural hematomas in the context of platelet dysfunction, with bleeding cessation achieved through platelet transfusion.