In Alpha Thalassemia, what does the presence of HbH indicate?

The presence of HbH in Alpha Thalassemia indicates a condition of moderate anemia that is associated with low mean corpuscular volume (MCV). HbH is a tetrameric form of hemoglobin composed of beta chains and is formed when there is a significant reduction in alpha globin chain production due to gene deletions or mutations. This imbalance leads to a specific type of anemia characterized by the presence of HbH on electrophoresis.

In this scenario, patients typically experience mild to moderate anemia, coupled with an MCV that is lower than normal. This is a consequence of the ineffective erythropoiesis and the presence of the abnormal hemoglobin which causes red blood cells to be smaller (microcytic). HbH disease is more severe than the silent carrier state and manifests with symptoms that can include moderate anemia.

Understanding this distinction helps in diagnosing and managing patients with Alpha Thalassemia, as it highlights the need for monitoring and potential interventions for those presenting with HbH.