Color Atlas of Hematology - Practical Microscopic and Clinical ...

144 Erythrocyte and Thrombocyte AbnormalitiesCytomorphological Anemias with ErythrocyteAnomaliesMicrospherocytosis This corpuscular form of hemolysis is characterizedby dominant genetic transmission, splenomegaly, and a long uneventfulcourse with occasional hemolytic crises. Blood analysis shows erythrocyteswhich appear strikingly small in comparison with leukocytes. Thecentral light area is absent or only faintly visible, since they are sphericalin cross-section rather than barbell-shaped. The abnormal size distributioncan be measured in two dimensions and plotted using Price–Jonescharts. Close observation of the morphology in the smear (Fig. 50) is particularlyimportant, because automated blood analyzers will determinea normal cell volume. The extremely reduced osmotic resistance of theerythrocytes (in the NaCl dilution series) is diagnostic. Coombs test isnegative.Stomatocytosis is an extremely rare hereditary condition. Stomatocytesare red cells with a median streak of pallor, giving the cells a “fish mouth”appearance. A few stomatocytes may be found in hepatic disease.Hemoglobinopathies (see also thalassemia, p. 138). Target cells arefrequently present (Fig. 47).In addition to target cells, smears from patients with sickle cell anemiamay show a few sickle-shaped erythrocytes, but more usually these onlyappear under conditions of oxygen deprivation (Fig. 50). (This can beachieved by covering a fresh blood droplet with a cover glass; a droplet of2% Na 2 S 2 O 4 may be added). Sickle cell anemia is a dominant autosomal recessivehemoglobinopathy and is diagnosed by demonstrating the HbSband in Hb-electrophoresis. Homozygous patients with sickle cell anemiaalways suffer from chronic normocytic hemolysis. If provoked by oxygendeficiency or infections, severe crises may occur with clogging of the microvasculatureby aggregates of malformed erythrocytes. Patients who areheterozygous for sickle cell anemia have the sickle cell trait but do not displaythe disease or its symptoms. These can, however, be triggered by verylow oxygen tension. Sickle cell anemia is quite often combined with otherhemoglobinopathies, such as thalassemia.Schistocytosis (Fragmentocytosis) If, in acquired hemolytic anemia, someof the erythrocytes are fragmented and have various irregular shapes(eggshell, helmet, triangle, or crescent; Fig. 49), this may be an indicationof changes in the capillary system (microangiopathy), or else of disseminatedintravascular coagulopathy (DIC). Microangiopathic hemolytic anemiasdevelop in the course of thrombotic thrombocytopenic purpura (TTP,Moschcowitz disease) and its related syndromes: in children (hemolyticuremic syndrome, HUS); in pregnant women (HELLP syndrome); or inpatients with bone marrow metastases from solid tumors.