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In Europe, the incidence of new cases of RARS is estimated at around 1 per 100,000 people per year but precise values are not available. Incidence increases with age by a factor of around 10 in those aged 70 and over.

It occurs mainly in elderly people or people of late middle age at a rate that varies somewhat around the world.

The cause is not known. It appears to be a clonal disorder arising from a haemopoetic stem cell abnormality but is not associated with any particular cytogenetic change except for a few reports of chromosomal rearrangements involving Xq13.

Diagnosis requires examination of both blood and bone marrow, investigation into possible secondary acquired causes and careful attention to any family and clinical history that would suggest an inherited type of sideroblastic anaemia (see these terms).

RARS can be separated from other categories of MDS by the presence in the bone marrow of more than 15% of ringed sideroblasts in the erythroid cells, an absence of dysplasia in the other cell lineages and a low percentage of myeloid blasts (<5%).

Treatment is mainly supportive and directed towards alleviating the symptoms of anaemia and avoidance or treatment of iron overload that results from any blood transfusion. Regular full blood count monitoring is important.

The risk of transformation to leukaemia is low (between 5 to 10% at 10 years in those with a normal karyotype and no dependence on blood transfusion) compared with other groups of MDS (for example 50% at 8 months in the group with thehighest risk), and the prognosis is good. Life expectancy in those over 70 years of age with RARS may be no different to that of the general population. The development of bi-lineage or multi-lineage dysplasia, the emergence of cells which are karyotypically abnormal, or an increased dependency on blood transfusions herald a worse prognosis and may indicate more vigorous intervention.