Leucostasis

Leukostasis is a life-threatening emergency caused by a disturbance in microcirculation due to leukocytes (Herold 2025 / Antwerpes 2026).

High white blood cell counts can lead to three main complications:

• Disseminated intravascular coagulation (DIC)
• Tumor lysis syndrome (TLS)
• Leukostasis (Giammarco 2017)

See: Leukemic Thrombi

The incidence of leukostasis varies depending on the specific type of leukemia:

• acute myeloid leukemia 10–20%, mainly in the context of monocyte-differentiated morphological subtypes.
• acute lymphocytic leukemia: 10–30%
• Chronic lymphocytic leukemia: only rarely, since the lymphocytes are small and white blood cell counts are usually below 400,000/µl.
• Chronic myeloid leukemia: despite pronounced leukocytosis due to a left shift, it is rare (Atta 2023).

Leukostasis can occur in association with leukemia (Atta 2023).

The pathophysiology is multifactorial. On the one hand, leukemic blasts are larger and less deformable; on the other hand, there is endothelial damage caused by proinflammatory cytokines and increased interaction between leukemic cells and endothelial adhesion molecules. Local hypoxia and cell aggregation also promote a “sludge” phenomenon in the capillaries (Antwerpes 2026).

Fever is common (Kreuzer 2016), affecting approximately 80% of patients; in addition, signs of myocardial ischemia, right-sided heart strain, acute ischemia of the extremities, priapism, mesenteric infarction, or worsening renal function (Marx 2024). Other symptoms are organ-specific:

• Pulmonary symptoms:

Pulmonary symptoms may include mild exertional dyspnea, as well as dyspnea, tachypnea, cyanosis, and even respiratory failure (Antwerpes 2026).

• Neurological symptoms:

These may begin insidiously and progress within hours, presenting as somnolence, dizziness, confusion, seizures, and coma (Antwerpes 2026), tinnitus, headaches, and vision loss (Kreuzer 2016).

• Ophthalmological symptoms:

These include diplopia or visual disturbances. On examination, papilledema and congested retinal veins are present (Antwerpes 2026).

The diagnosis is based on the patient's medical history, laboratory tests, and organ-specific examinations:

• Lungs:

Chest X-ray, blood gas analysis (Antwerpes 2026). These reveal interstitial or alveolar infiltrates (Atta 2023).

• CNS:

In addition to a neurological examination, cranial imaging is also performed (Antwerpes 2026).

• Eyes:

Funduscopy (Antwerpes 2026).

The likelihood of leukostasis is determined using the Novotny score (). 216–220

• Novotny Score:
  • Possible: mild physical impairments, moderate fatigue
  • Likely: significant impairment and severe exhaustion
  • Very likely: severe impairments with dyspnea at rest and oxygen dependency, myocardial infarction, ischemic necrosis, priapism (Fleischmann 2018).

If marked leukocytosis occurs, the following may occur:

• Pseudohypoxemia (due to continued oxygen consumption by the leukocytes in the blood sample)
• Pseudohyperkalemia (due to leukocyte fragility resulting in potassium release) (Antwerpes 2026)

• Pulmonary Embolism
• Pneumonia
• Sepsis
• Leukemic pulmonary infiltration
• Acute lysis pneumonopathy
• ARDS
• Hyperviscosity syndrome associated with monoclonal gammopathy
• Leukemic meningeitis
• Cerebral hemorrhage or ischemia of other etiology
• Hyperleukosis: This condition is characterized by extremely high white blood cell counts, but does not necessarily result in symptoms (Antwerpes 2026)

Disorders affecting target organs, particularly the lungs and the brain, due to reduced perfusion; the eyes or other organs are affected less frequently (Antwerpes 2026)

The most important therapeutic measure is immediate cytoreduction. Therapeutic measures for treating the underlying disease should be continued (Antwerpes 2026).

The following are used for cytoreduction:

• Extracorporeal leukapheresis:

This reduces leukocyte counts by 20–50%. Some studies report a reduction in early mortality; however, the treatment has no effect on overall mortality (Kreuzer 2016).

• Cytoreductive chemotherapy:

e.g., with hydroxycarbamide (hydroxyurea): The initial daily dose is 50–100 mg/kg body weight/day, i.e., 1–2 g every 6 hours. This results in a 50–80% reduction in white blood cell counts within 24–48 hours (Kreuzer 2016).

Further therapeutic measures may include:

• early transfer to the intensive care unit
• early initiation of noninvasive ventilation
• dexamethasone
• restrictive transfusion strategy
• moderate volume therapy (Kreuzer 2016)
• Empirical antimicrobial therapy is recommended in all symptomatic cases (Marx 2024). 

Early mortality is approximately 40% when the central nervous system is involved and approximately 30% when the lungs are involved (Atta 2023). There is no direct correlation between cell count and mortality rate (Marx 2024). 

Patients die primarily from acute ischemia or acute hemorrhage (Fleischmann 2018).

1. Antwerpes F et al. (2026) Leukostasis syndrome. Doc Check Flexikon https://flexikon.doccheck.com/de/Leukostasesyndrom
2. Atta J, Ajib S A, Froh S (2023) Hematological and Oncological Emergencies. E.Medpedia https://www.springermedizin.de/emedpedia/detail/the-intensive-care-medicine/hematological-and-oncological-emergencies?epediaDoi=10.1007%2F978-3-642-54675-4_107
3. Fleischmann T (2018) Clinical Emergency Medicine Cases: The 100 Most Important Diagnoses. Elsevier Urban & Fischer Verlag, Germany, pp. 216–220
4. Giammarco S, Chiusolo P, Piccirillo N, Di Giovanni A, Metafuni E, Laurenti L, Sica S, Pagano L (2017) Hyperleukocytosis and leukostasis: management of a medical emergency. Expert Rev Hematol. 10 (2): 147–154
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8. Marx G, Muhl E, Zacharowski K, Zeuzem S (2024) Intensive Care Medicine. Springer Verlag Deutschland 1658–1659