A 37-year-old man presents with isolated thrombocytopenia: normal Hb, WBC; platelets 45k with high bleeding time and normal PT. Bone marrow shows increased megakaryocytes. What is the most likely diagnosis?

A 37-year-old man presents with isolated thrombocytopenia: normal Hb, WBC; platelets 45k with high bleeding time and normal PT. Bone marrow shows increased megakaryocytes. What is the most likely diagnosis?

• A. Thrombotic thrombocytopenic purpura
• B. Disseminated intravascular coagulation
• C. Von Willebrand disease
• D. Immune thrombocytopenic purpura

Answer: (D)

Isolated thrombocytopenia with normal hemoglobin and white count, a prolonged bleeding time, normal coagulation tests, and bone marrow showing increased megakaryocytes points to platelet destruction in the periphery with compensatory production. The bone marrow responds by boosting megakaryocyte formation, which explains the elevated megakaryocytes despite low platelets. This pattern is characteristic of immune thrombocytopenic purpura, where autoantibodies target platelets and lead to their accelerated clearance, usually in the spleen, resulting in a low platelet count and bleeding tendency. Other conditions would present differently. Thrombotic thrombocytopenic purpura typically has microangiopathic hemolytic anemia with a low hemoglobin and neurological or renal findings. Disseminated intravascular coagulation shows abnormal coagulation tests (prolonged PT/aPTT), low fibrinogen, and widespread consumption of clotting factors. Von Willebrand disease involves bleeding due to defective platelet function or von Willebrand factor deficiency, often with a normal platelet count and sometimes prolonged bleeding time, but without the marrow megakaryocytic hyperplasia seen in peripheral destruction.

Isolated thrombocytopenia with normal hemoglobin and white count, a prolonged bleeding time, normal coagulation tests, and bone marrow showing increased megakaryocytes points to platelet destruction in the periphery with compensatory production. The bone marrow responds by boosting megakaryocyte formation, which explains the elevated megakaryocytes despite low platelets. This pattern is characteristic of immune thrombocytopenic purpura, where autoantibodies target platelets and lead to their accelerated clearance, usually in the spleen, resulting in a low platelet count and bleeding tendency.

Other conditions would present differently. Thrombotic thrombocytopenic purpura typically has microangiopathic hemolytic anemia with a low hemoglobin and neurological or renal findings. Disseminated intravascular coagulation shows abnormal coagulation tests (prolonged PT/aPTT), low fibrinogen, and widespread consumption of clotting factors. Von Willebrand disease involves bleeding due to defective platelet function or von Willebrand factor deficiency, often with a normal platelet count and sometimes prolonged bleeding time, but without the marrow megakaryocytic hyperplasia seen in peripheral destruction.