138 Erythrocyte and Thrombocyte Abnormalities

Hypochromic Anemia with Hemolysis

Thalassemias

A special form of hypochromic anemia mostly affecting patients of Mediterranean descent presents with normal erythrocyte count, decreased MCH, and clinical splenomegaly. The smear displays erythrocytes with central hemoglobin islands (target cells). These cells do not necessarily predominate in the CBC: the most revealing field views show at most 50% target cells in addition to clear anisocytosis and frequent basophilic stippling. Occasional normoblasts give a general indication of increased erythropoiesis. Although target cells are also nonspecific, since they can occur in such conditions as severe iron deficiency or obstructive jaundice, this overall picture should prompt hemoglobin electrophoresis. The sample consists of ACD-stabilized blood at 1:10 dilution. A significant increase in the HbA2 fraction confirms a diagnosis of thalassemia minor, the heterozygous form of the disease. Thalassemia major, the homozygous variant, is far rarer and more serious. In this form of the disease, in addition to the target cells, the CBC shows a marked increase in red precursor cells. Hbelectrophoresis shows a predominance of HbF (the other hemolytic anemias are usually normochromic, see p. 140).

Hypochromic anemia without iron deficiency, sometimes with target cells, suggests thalassemia

a b

c

Fig. 47 Thalassemia. a Thalassemia minor: often no target cells, but an increase in the number of small erythrocytes (shown here in comparison with a lymphocyte), so that sometimes there is no anemia. b More advanced thalassemia minor: strong anisocytosis and poikilocytosis (1), basophilic stippling (2), and sporadic target cells (3). c Thalassemia major: erythroblasts (1), target cell (2), polychromatic erythrocytes (3), and Howell–Jolly bodies (4) (in a case of functional asplenia). Lymphocyte (5) and granulocyte (6).

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