What is the most likely cause of pancytopenia in a patient with alcoholic cirrhosis and portal hypertension?

Pancytopenia, which is the reduction of red blood cells, white blood cells, and platelets, can occur in patients with alcoholic cirrhosis and portal hypertension due to hypersplenism. In this condition, portal hypertension leads to engorgement of the spleen, resulting in increased sequestration of blood cells within the spleen.

As the spleen enlarges, its function in filtering and destroying blood cells becomes more pronounced, leading to a decrease in circulating blood cell counts. The liver's inability to produce sufficient amounts of necessary proteins, including thrombopoietin (which regulates platelet production), compounds this issue, contributing further to the decreases in red blood cells and platelets.

While disseminated intravascular coagulation can lead to changes in blood counts, it typically does not cause the sustained reduction seen in pancytopenia as a primary condition. Iron deficiency and vitamin B1 deficiency, while they can lead to specific types of anemia or other hematological changes, are less directly associated with the broad spectrum of blood cell reductions seen in hypersplenism related to portal hypertension.