What condition is characterized by an excess number of red blood cells?

Polycythemia is characterized by an excess number of red blood cells (RBCs) in the bloodstream. This condition leads to an increase in blood viscosity, which can affect circulation and lead to complications such as hypertension and increased risk of thrombosis.

In polycythemia, the body produces a higher-than-normal volume of red blood cells, which can occur for various reasons, including chronic hypoxia, genetic mutations, or other underlying health issues. This condition is important to recognize in clinical practice, as it can significantly impact a patient's health and may require specific management strategies.

The other conditions listed focus on different aspects of blood health. Hemophilia involves a deficiency in clotting factors leading to excessive bleeding. Anemia is characterized by a deficiency in red blood cells or hemoglobin, resulting in a reduced oxygen-carrying capacity of the blood. Thrombocytopenia is the condition where there is a lower than normal number of platelets in the blood, affecting the body's ability to clot effectively. Understanding these distinctions is crucial for proper diagnosis and treatment in health care.