Haema synthesis during pyridoxine therapy in two families with different types of hereditary sideroblastic anaemia.

The activity of delta-aminolaevulinic acid synthase (ALA-S) as well as the concentrations of coproporphyrin and protoporphyrin in peripheral red blood cells were examined in 2 sisters and in 2 brothers with hereditary sideroblastic anaemias (HSA) of different types. The measurements were done before and during treatment by pyridoxal-5-phosphate (PLP) and/or pyridoxine chloride. Previous family studies indicated an X chromosome linked HSA in the 2 brothers, whereas the precise mode of inheritance in the 2 sisters has not been established. Previous and present studies have revealed no characteristic defect in haema synthesis in the 2 sisters and their treatment by PLP or pyridoxine produced no haematologic response although a slight stimulation of haema synthesis was observed. In contrast, the 2 brothers showed decreased activity of ALA-S and decreased protoporphyrin concentration in peripheral red blood cells. After treatment by PLP and/or pyridoxine the ALA-S activity was restored to normal. Corresponding to the stimulation of haema synthesis a partial haematological response was observed in both brothers. Stopping and restarting of pyridoxine therapy in one brother confirmed the above results. These observations indicate the presence of two genetically and biochemically different types of HSA and help us to understand the varying response to pyridoxine therapy in this rare disorder.