One of the commonest types of anaemia, particularly in hospital patients, is the anaemia of chronic disease, occurring in patients with chronic infections such as infective endocarditis and tuberculosis and osteomyelitis in developing countries, chronic inflammatory diseases such as rheumatoid arthritis, systemic lupus erythematosus (SLE) and polymyalgia rheumatica and in patients with malignant disease. There is decreased release of iron from the bone marrow to developing erythroblasts, an inadequate erythropoietin response to the anaemia and decreased red cell survival. The exact mechanisms responsible for these effects are not clear but they seem to be mediated by inflammatory cytokines such as IL-1, tumour necrosis factor and interferons. The serum iron is low and the TIBC is also low. Serum ferritin is normal or raised. There is stainable iron present in the bone marrow and, therefore, patients do not respond to iron therapy. However, iron is not seen in the developing erythroblasts. Treatment is, in general, that of the underlying disorder, although trials are being carried out with recombinant erythropoietin in some patients, for example those with rheumatoid arthritis.
Sideroblastic anaemias are inherited or acquired disorders characterized by a refractory anaemia, a variable number of hypochromic cells in the peripheral blood, and excess iron and ring sideroblasts in the bone marrow. The presence of ring sideroblasts is the diagnostic feature of sideroblastic anaemia; there is disordered accumulation of iron in the mitochondria of erythroblasts due to disordered haem synthesis. A ring of iron granules is formed round the nucleus that can be seen with Perls’ reaction. The blood film is often dimorphic; ineffective haem synthesis is responsible for the microcytic hypochromic cells.
Sideroblastic anaemias can be classified as shown. Primary acquired sideroblastic anaemia is one of the myelodysplastic syndromes.
Some patients respond when drugs or alcohol are withdrawn if these are the causative agents. In some cases, particularly the inherited type, there is a response to pyridoxine. Treatment with folic acid may be required to treat accompanying folate deficiency.
The causes, clinical features and treatment are . The characteristic haematological features include:
SIDEROBLASTIC ANAEMIA, due to inhibition by lead of several enzymes involved in haem synthesis including 8-aminolaevulinic acid synthetase.
HAEMOLYSIS, which is usually mild, due to damage to the red cell membrane.
PUNCTATE BASOPHILIA (the blood film shows red cells with small, Tound, blue particles), due to aggregates of RNA in red cells due to inhibition by lead of pyrimidine- 5-nucleotidase, which normally disperses residual RNA to produce a diffuse blue staining seen in reticulocytes on blood films (polychromasia).