The contribution of extramedullary hematopoiesis to hepatomegaly in anemic hydrops fetalis: a study in alpha-thalassemia hydrops fetalis.

Massive hepatomegaly is a common finding in hydrops fetalis (HF) arising from hemoglobinopathies. It has been suggested that extramedullary hematopoiesis, which is markedly increased in response to anemia, plays a principal role in hepatomegaly via sinusoidal obstruction and distortion of the intrahepatic architecture. To test this concept, the authors compared 20 cases of α-thalassemia (hemoglobin Bart, 15 cases; hemoglobin H, 5 cases) with 19 cases of HF arising from other causes and 39 control nonhydrops cases. The mean liver weight in α-thalassemia cases was significantly heavier than in control cases and in hydrops fetalis cases due to other causes (P < 0.01). This was not explainable on the basis of extramedullary hematopoiesis (erythropoiesis or myelopoiesis) or hemosiderin deposition, since cases of HF from other causes, especially related to anemia, showed similar findings to α-thalassemia cases. While these processes no doubt contribute to hepatic weight, the major factor would still be high-output cardiac failure causing hepatic congestion.