Abstract
Erythroid colony (EC) formation and heme biosynthesis were studied in marrow cultures of a 2 year old girl with severe CSA and neutropenia. Bone marrow showed micronormoblastic erythroid hyperplasia, ringed sideroblasts and decreased granulopoeisis. The patient had not responded to hematinics. and prednisone. EC formation was determined in plasma clot (pc) and methyl cellulose (mc) culture systems after 7 days incubation by benzidine staining and expressed as CFUE/8×105 marrow cells. In pc cultures, EC(140) were fewer than normal adult controls (1100).However, cultures in me resulted in exuberant EC growth (1400). Good EC formation (900) also occurred without added erythropoeitin (ep), in contrast to no growth in controls. Addition of hemin stimulated EC formation (2000) and reversed pyridoxal PO4 inhibition. δ-aminolevulinic acid (ALA) synthetase activity of marrow itself was substantially decreased and heme oxygenase was increased. However, in me culture ALA synthetase, ALA dehydratase, C- 14ALA incorporation into heme and H-3 leucine incorporation into protein were normal and increased by addition of hemin. This patient's excellent capacity to synthesize hemoglobin and form EC in me culture, even in the absence of added ep, suggests that CSA may result from an unfavorable marrow microenvironment.
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