161.The answer is a.(Junqueira, pp 224–226. Kasper, pp 330–335. Kumar,
pp 622–628.)Iron deficiency leads to anemia with the presence of smaller,
pale-staining erythrocytes (microcytic, hypochromatic). Hyperchromatic,
macrocytic anemia results from vitamin B 12 deficiency(answers b and e).
The presence of spherical rather than biconcave erythrocytes is known as
spherocytosis (answer d).The RBC membrane undergoes deformation
due to the inability of ankyrin to bind spectrin. The shape change results in
trapping in the splenic sinusoids and excessive destruction of red blood
cells in that organ. Poikilocytosis is the generic term for abnormally shaped
erythrocytes (answer c).Hereditary elliptocytosis and hereditary poikilo-
cytosis are inherited diseases in which there is RBC membrane fragility and
abnormal shape due to spectrin mutations. Mutations in Band 3 (anion
exchanger 1) result in RBCs that are hyperchromatic with poikilocytosis.
162.The answer is c.(Kasper, pp 329–330, 1658. Junqueira, pp 240, 242,
373.)Normal hematocrit for a woman is 37 to 47%. The most likely cause
of the anemia is renal failure leading to decreased production of the kidney-
derived red blood cell growth factor, erythropoietin (answers a and b).In
the initial stages of renal failure the kidneys will increase their production
of erythropoietin, but as renal damage continues, the cells that produce
this factor are destroyed. Therefore, there are initially increased levels of
reticulocytes (immature red blood cells) in the bloodstream, but this is later
reversed, as in the anemia of renal disease, low production of reticulocytes
is a hallmark of the disease. Although the patient may have decreased estro-
gen levels, estrogen decreases hematocrit (answers d and e).Also, women
who are pregnant (third trimester) can have slightly decreased hematocrits
[37±6 (third trimester women) vs. 40 ±6 (adult women) and 42 ± 6
(postmenopausal women)]. However, this patient had a negative preg-
nancy test. Administration of recombinant erythropoietin (EPO) is the pre-
ferred treatment for anemia caused by advanced renal disease. Generally,
EPO is administered if the hematocrit is less than 30%. Erythropoietin is
synthesized by the peritubular (interstitial) cells of the kidney cortex,
stimulates the differentiation of cells from the erythrocyte colony–forming
units (E-CFUs), and the differentiation and release of reticulocytes from the
bone marrow. Colony-forming units (CFUs) are distinct cell lineages
derived from pluripotential stem cells in the bone marrow.
266 Anatomy, Histology, and Cell Biology