ABNORMAL HEME-BIOSYNTHESIS IN THE CHRONIC ANEMIA OF RHEUMATOID-ARTHRITIS

Objectives-The chronic microcytic anaemia of rheumatoid arthritis (RA) occurs despite the presence of adequate reticulo-endothelial iron sto res. The red cell microcytosis is evidence of impaired haemoglobin pro duction. This study has examined possible abnormalities of erythroid h aem biosynthesis that may contribute to the anaemia. Methods-5-Aminola evulinate (ALA) synthase and ferrochelatase activities were assayed in whole bone marrow and in purified erythroblasts from patients with RA and in control subjects. Ah patients were iron replete with demonstra ble iron in the bone marrow. Results-ALA synthase activity was signifi cantly reduced in both whole bone marrow and purified erythroblasts fr om patients with the anaemia of RA. Erythrocyte protoporphyrin levels were raised in nine of 12 patients tested while ferrochelatase activit y was normal. Conclusion-These abnormalities provide absolute evidence of abnormal erythroblast haem biosynthesis and iron metabolism in the anaemia of RA and most Likely reflect decreased ALA synthase mRNA tra nslation and some abnormality of erythroblast iron transport. Further studies using highly purified erythroblast populations will attempt to identify the causal factors leading to this abnormal erythroblast met abolism.