Disordered haem synthesis resulting in abnormal accumulation of iron within red blood cells.
Haem synthesis is abnormal with a failure of iron incorporation. There is accumulation of iron in the mitochondria of erythroblasts, which stain as a ring around the nucleus (ring sideroblasts). Sideroblastic anaemia may be congenital or acquired:
· Congenital X-linked disease.
· Primary acquired sideroblastic anaemia is one of the myelodysplastic syndromes.
· Secondary acquired sideroblastic anaemia may be caused by drugs (e.g. isoniazid) or toxins such as lead or alcohol.
Patients initially present with symptoms and signs of anaemia. As sideroblastic anaemia results in a microcytic hypochromic anaemia, it may be misdiagnosed as iron deficiency. The anaemia is however refractory to iron supplementation.
· The full blood count and film may reveal diamorphic red cells, i.e. there are two populations of cells – one normal sized and a population of microcytic hypochromic cells.
· Serum iron and ferritin are normal or raised.
· Perl’s staining of bone marrow samples shows a ring of iron around the nucleus in erythrocyte precursors. The presence of these ring sideroblasts are diagnostic.
Congenital sideroblastic anaemia may respond to pyridoxine. Primary acquired sideroblastic anaemia is treated as for myelodysplastic syndrome. In secondary acquired sideroblastic anaemia any causative agent should be removed where possible.