[Secondary sideroblastic anemia caused by long term administration of anti-tuberculous agents including isoniazid]

A 54 year-old man, who had been treated for several years with isoniazid, was transferred to our hospital because of intractable pulmonary tuberculosis. He was given several anti-tuberculous agents including INH, CS and/or PZA for a long period of time without improvement of the pulmonary tuberculosis. After 7 years' treatment with INH, hypochromic microcytic anemia developed. Parenteral administration of iron preparation failed to improve the anemia. The bone marrow findings revealed erythroid hyperplasia and a few erythroblasts showed megaloblastic change. The bone marrow iron staining revealed increased sideroblasts of which 88% were ringed-form. INH was then discontinued and pyridoxal phosphate was administered with rapid complete improvement of the anemia. INH is well known as a causative agent for acquired secondary sideroblastic anemia, however only one case of INH-induced sideroblastic anemia has been reported in Japan. This is the second reported Japanese case of INH-induced secondary sideroblastic anemia, which appears to be a very rare condition because of genetically determined rapid acetylation of INH in Japanese.