Knizocytes or bridge cells, one of which is seen at the point of the arrow, are cells with hemoglobin across the light central area. With scanning electron microscopy the red cells have two concavities instead of one. Knizocytes are most characteristic of thalassemia syndromes. The blood shown here was from a peitent with homozygous B-thalassemia, also called thalassemia major. The blood of such patients is distinguished by marked anisocytosis, marked poileptocytes or thin cells. The red cells may appear almost macrocytic on fixed films, but when the corpuscular volume is calculated, they are actually microcytic because they are thin. Heterozygous thalassemia or thalassemia trait cannot be distinguished from iron deficiency by a blood smear only.
Course Section: 01. Description of Red Blood Cells
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