What is the result of having all four alpha globin genes deleted in alpha thalassemia?

When all four alpha globin genes are deleted in alpha thalassemia, the result is a condition known as hydrops fetalis. This severe condition typically occurs when there is a complete absence of functional alpha globin chains, which is critical for the formation of hemoglobin. Without any alpha globin chains, the fetus cannot produce normal hemoglobin (Hb A) or any viable forms that would support adequate oxygen transportation.

Hydrops fetalis is characterized by fluid accumulation in various compartments of the body, indicating severe anemia and resultant heart failure due to the inadequate oxygen supply to the fetal tissues. The lack of alpha globin leads to a significant imbalance with excess beta globin, which forms unstable tetrameric structures (Hb Bart’s or Hb H, depending on the quantity of remaining beta globin). These structures are not effective in carrying oxygen and contribute to the severe clinical manifestations associated with hydrops.

In summary, the deletion of all four alpha globin genes leads to hydrops fetalis due to the profound anemia and circulatory compromise that occurs in the fetus, making it a life-threatening condition requiring careful management and often intervention.