Acquired Idiopathic Sideroblastic Anemia
A rare myelodysplastic syndrome (MDS) characterized by ineffective hemopoiesis affecting one or more blood cell lineages (myeloid, erythroid or megakaryocytic) leading to peripheral blood cytopenias and an increased risk of developing leukaemia.
Epidemiology
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.
Clinical description
It occurs mainly in elderly people or people of late middle age at a rate that varies somewhat around the world.
Etiology
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.
Diagnostic methods
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).
Differential diagnosis
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%).
Management and treatment
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.
Prognosis
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.