Aplastic anemia in Taiwan and its etiological factors.

Ninety patients with a strict diagnosis of aplastic anemia were observed during a 4-year period. The incidence of aplastic anemia is estimated to be much higher here than in western countries. A disproportionately large number of young males were noted among our patients. Two cases were congenital. One case presented a past history of paroxysmal nocturnal hemoglobinuria. The etiology of 8 cases (8.9%) could be attributed to drugs and/or chemicals. In the remaining 79 cases (87.8%), the causes of the disease were unknown. The carrier rate of the hepatitis B surface antigen in the patients with aplastic anemia was similar to that of the general population, and chronic hepatitis B infection was not considered a major etiological factor. Coexistence of abnormal liver functions at the initial presentation was noted in 21.9% of the patients. Exposure to unknown drugs by self-medication was possibly one of the major causes of the high incidence of aplastic anemia and the associated abnormal liver functions in our patients.