Hepatitis B Leading to Megaloblastic Anemia and Catastrophic Peripheral Thrombocytopenia

Hepatitis B virus (HBV) typically causes chronic hepatitis, cirrhosis, and hepatocellular carcinoma. It is associated with a variety of extrahepatic complications. We herein, present a rare extrahepatic complication of HBV infection. A 32-year man presented with melena, bleeding from gums and fever. Peripheral blood examination revealed anemia, macrocytosis and severe thrombocytopenia. His hepatitis B surface antigen (HBsAg) was positive but deoxyribonucleic acid (HBV DNA) by polymerase chain reaction (PCR) was negative. Other hepatitis, human immune deficiency virus (HIV), dengue, and autoimmune serology were negative. Bone marrow examination revealed megaloblastic erythropoiesis. There was mild to moderate reduction of megakaryocytes in bone marrow, which was not compatible with severe peripheral thrombocytopenia. His response to cyanocobalamin and folic acid was remarkable for myeloid cell lines and moderate for erythroid cell lines, but poor to platelet counts. Platelet counts gradually improved to safe limits with eltrombopag, likely reflecting autoimmune pathogenesis for thrombocytopenia. This case report highlights multiple targets of HBV infection with associated multiple pathogenetic mechanisms.