macrothrombocytes

Macrothrombocytes are abnormally large platelets observed in the peripheral blood. They are typically associated with macrothrombocytopenia, a condition characterized by low platelet counts and enlarged platelets. On a blood smear, platelets appear larger than normal and may appear pale.

Macrothrombocytopenia can be inherited in several syndromes. Bernard-Soulier syndrome is caused by defects in the GPIb-IX-V complex, leading to giant platelets and thrombocytopenia with bleeding. MYH9-related diseases (including May-Hegglin anomaly, Fechtner syndrome, and Sebastian syndrome) feature macrothrombocytopenia and can include neutrophil inclusions and, in some cases, nephritis or deafness. Other rare genetic causes involve mutations affecting megakaryocyte maturation.

Pathophysiology: impaired platelet production and fragmentation during megakaryopoiesis results in large platelets; platelet counts are reduced, and platelet function can be abnormal. Bleeding tendency varies from mild to moderate.

Diagnosis: complete blood count shows thrombocytopenia with large platelets; blood smear confirms macrothrombocytes. Flow cytometry or genetic testing can identify underlying defects in Bernard-Soulier (GPIb-IX-V) or MYH9-related disease. Additional tests may evaluate organ involvement or neutrophil inclusions.

Management: treatment is directed at the underlying cause and bleeding risk. In symptomatic cases, platelet transfusions may be used for significant bleeding; desmopressin can help in mucosal bleeding; avoid routine antiplatelet drugs; genetic counseling may be offered.