Coproporphyrinogen oxidase activity and porphyrin concentrations in peripheral red blood cells in hereditary...

The activity of coproporphyrinogen oxidase and the concentrations of coproporphyrin and protoporphyrin (measured by HPLC) in peripheral red blood cells were established in 2 families with different types of hereditary sideroblastic anaemia. 2 males and 4 females were members of a family with an X-chromosome-linked and pyridoxine-responsive HSA, and 3 females were members of another family where the mode of inheritance is not clear and where pyridoxine did not produce a haematological response. Coproporphyrinogen oxidase activity was normal in 8 of 9 patients and slightly decreased only in 1 patient. All patients had normal red cell coproporphyrin concentrations, but red cell protoporphyrin concentration was decreased in 4 patients. These findings indicate that in vivo haem synthesis was not impaired at the step of coproporphyrinogen oxidase, hence enzymatic defects in earlier steps of haem synthesis are more evident. Earlier suggestions of impaired haem synthesis at this level, based on observed increased concentrations of coproporphyrin in peripheral red blood cells might be explained by the use of unspecific methods.