Seema Dawood: Microscopic Findings, Pathophysiology and Associated Conditions of Thrombophagocytosis
Seema Dawood, Medical Laboratory Technologist at The Aga Khan University Hospital, shared a post on LinkedIn:
“Thrombophagocytosis
Thrombophagocytosis is a phenomenon in which white blood cells – most commonly Monocytes or Macrophages (histiocytes) – engulf platelets within their cytoplasm.
Microscopic Findings
- Platelets are observed inside the cytoplasm of macrophages or histiocytes
- Commonly associated with thrombocytopenia (low platelet count)
Pathophysiology:
Thrombophagocytosis results from severe immune system activation, leading to excessive macrophage activation.
Activated macrophages abnormally phagocytose blood cells, including platelets.
Associated Conditions
- Hemophagocytic lymphohistiocytosis (HLH) – most common and clinically significant
- Severe infections (e.g., Dengue fever, EBV, CMV, sepsis)
- Autoimmune diseases (e.g., systemic lupus erythematosus; SLE)
- Certain Hematologic malignancies
Represents a marker of severe immune activation
When found together with:
- Thrombocytopenia
- Multilineage cytopenia
- Persistent fever and hepatosplenomegaly
HLH should be strongly suspected, and further evaluation is urgently required.
HLH and Thrombophagocytosis
Hemophagocytic lymphohistiocytosis (HLH) is a disorder characterized by uncontrolled and severe immune activation.
It results from impaired function of NK cells and cytotoxic T lymphocytes, leading to:
- Failure to regulate immune responses
- Persistent activation of macrophages
- In HLH, macrophage activation is excessive and sustained
Activated macrophages perform hemophagocytosis, engulfing various blood cells:
- Platelets – Thrombophagocytosis
- Red blood cells – Erythrophagocytosis
- White blood cells – Leukophagocytosis
Therefore, thrombophagocytosis is one of the characteristic morphologic findings in HLH and supports the diagnosis when correlated with clinical and laboratory features.”

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