What condition is characterized by an abnormally low number of platelets in the blood?

The condition characterized by an abnormally low number of platelets in the blood is indeed thrombocytopenia. This hematological condition occurs when the platelet count falls below the normal range, which can lead to increased bleeding and bruising since platelets are crucial for blood clotting.

Thrombocytopenia can result from various factors, including bone marrow disorders, increased destruction of platelets, or certain medications. Managing thrombocytopenia typically involves treating the underlying cause and may include therapies to increase platelet counts.

On the other hand, anemia refers to a deficiency in red blood cells or hemoglobin in the blood, which affects oxygen transport rather than platelet count. Leukopenia means low white blood cell count, impacting the immune response rather than clotting functions. Erythrocytosis is a condition of elevated red blood cell mass, which increases blood viscosity but is unrelated to platelet levels. Thus, thrombocytopenia is the specific condition associated with low platelet counts, making it the correct answer.