Leukaemic thrombi

Chronic myeloid leukemia is characterized by the highest white blood cell counts compared to other types of leukemia. Hyperleukocytosis and leukostasis—that is, reduced tissue perfusion—can lead to leukemic thrombi (Herold 2025) and thus constitute a life-threatening hematologic emergency (Antwerpes 2026).

Hyperleukocytosis, defined as a white blood cell count exceeding 100,000/µl, can cause three main complications:

• disseminated intravascular coagulation
• tumor lysis syndrome
• leukostasis (Giammarco 2016)

Leukemic thrombi occur in approximately 30% of patients with hyperleukocytic AML and in patients with blast-type CML (Antwerpes 2026). In principle, however, they can occur in all forms of leukemia (Atta 2023).

The pathophysiology is multifactorial and is not solely related to the white blood cell count. Leukemic blasts can obstruct blood flow, but this is compounded by

• endothelial damage caused by cytokines
• increased interaction between leukemic cells
• local hypoxia
• cell aggregation in the capillaries (Antwerpes 2026)

Leukemic thrombi primarily affect the spleen, the central veins of the retina, the myocardium, and are associated with leukemic priapism (Herold 2025).

In terms of clinical symptoms, the symptoms of the underlying disease are the primary concern. The symptoms caused by leukemic thrombi are evident in

• pulmonary involvement as dyspnea, tachypnea, and cyanosis
• neurological involvement as somnolence, dizziness, confusion, headache, intracerebral hemorrhage, ischemic lesions, seizures, and coma;
• ophthalmic symptoms, such as diplopia, visual disturbances, papilledema, and retinal vein stasis
• in cases of renal involvement, by renal dysfunction (Antwerpes 2026)

The diagnosis is made based on the patient’s medical history, organ-specific examinations (such as blood gas analysis, X-rays, neurological examinations, cranial imaging, eye examinations, etc.), and laboratory findings (Antwerpes 2026).

In terms of differential diagnosis, the following should be ruled out in particular:

• Pneumonia
• Sepsis
• Leukemic pulmonary infiltrates
• Pulmonary embolism
• Leukemic meningeitis
• ARDS
• Cerebral hemorrhage or ischemia of other etiology (Antwerpes 2026)

In addition to treating the underlying disease, cytoreductive leukapheresis should be performed immediately after diagnosis (Antwerpes 2026 / Pottgießer 2019). This should not be performed only in cases of acute promyelocytic leukemia due to the high risk of bleeding (Antwerpes 2026).

In addition to leukapheresis, cytoreductive measures such as corticosteroids, hydroxyurea, and intravenous chemotherapy are also available (Macaron 2022).

Early mortality within the first week after diagnosis ranges from 20 to 40 percent; while there is no direct correlation between cell count and mortality rate, the prognosis for patients with neurological or respiratory symptoms is significantly worse (Atta 2023).

1. Antwerpes F et al. (2026) Leukostasis syndrome. Doc Check Flexikon https://flexikon.doccheck.com/de/Leukostasesyndrom
2. Atta J, Abdulfatah Ajib S, Froh S (2023) Hematological and oncological emergencies. https://www.springermedizin.de/emedpedia/detail/die-intensivmedizin/haematologische-und-onkologische-notfaelle?epediaDoi=10.1007%2F978-3-642-54675-4_107
3. Giammarco S, Chiusolo P, Piccririllo N, Di Giovanni A, Metafun E, Laurenti L, Sica S, Pagano L (2016) Hyperleukocystosis and leukostasis: management of a medical emergency. Expert Rev Hematol. 10 (2) 147–154
4. Herold G et al. (2025) Internal Medicine. Herold Verlag 103
5. Kasper D L, Fauci A S, Hauser S L, Longo D L, Jameson J L, Loscalzo J et al. (2015) Harrison’s Principles of Internal Medicine. McGraw-Hill Education
6. Macaron W, Sargsyan Z, Short N J (2022) Hyperleukocytosis and leukostasis in acute and chronic leukemias. Leuk Lymphoma. 63 (8) 1780–1791
7. Pottgießer T, Schorb E, Ophoven S (2019) 80 Cases in Internal Medicine: From Clinical Practice. Elsevier Urban & Fischer Verlag, Munich, pp. 323–324