Question 128
A 39-year-old female presents to her family physician with complaints of fatigue that has increased over the past 6 months. She is a runner and has had to cut back on her morning runs because of increased shortness of breath. A complete blood cell count reveals a hemoglobin of 8.3 g/dL, hematocrit of 24%, white blood cell count of 5200 cells/mm3, and platelet count of 300,000/mm3. The MCV is 70 fl. The reticulocyte production index (RPI) is <2. Of the following, what is the most likely mechanism for her presenting symptoms?
A. Splenic sequestration of red blood cells
B. Marrow infiltration by a non-neoplastic process
C. Decreased production of red blood cells
D. Antibody-mediated destruction of red blood cells
E. Decreased lifespan of red blood cells
Answer for Question 128
Answer: C (Decreased production of red blood cells)
Explanation: Given a slow developing anemia in a younger female, iron deficiency due to blood loss related to heavy menstrual or irregular menstrual bleeding is most likely. The low MCV confirms a microcytic anemia. The low reticulocyte production index indicates underproduction, such as would occur in an iron deficiency anemia, as not enough iron is available to produce red blood cells. While an antibody-mediated destruction of red blood cells could produce spherocytes, which would lead to a low MCV, the reticulocyte production index in a hemolytic anemia would be higher. With a decreased lifespan of red blood cells, such as in hereditary spherocytosis, the reticulocyte production index should be high in response to the red blood cell destruction. Marrow infiltration by a non-neoplastic process (e.g., sarcoidosis) would most likely affect all three cell lines, leading to leukopenia and thrombocytopenia as well as anemia.
Question 129
A 37-year-old female presents to her family physician with complaints of fatigue that has developed and been increasing over the past year. A review of systems indicates that she has been having heavier than normal menstrual periods for a little over a year. A complete blood cell count reveals a hemoglobin of 8.2 g/dL (normal: 12-16 g/dL), hematocrit of 24% (normal: 37-47%), a white blood cell count of 7.3 x 103 cells/mm3 (normal range: 4.5-11 x 103 cells/mm3), mean corpuscular volume of 67 fL (normal range: 80-100 fL), and platelet count of 280,000 cells/mm3 (normal range: 150-400,000/mm3). Of the following, which set of test results would confirm iron deficiency anemia?
Answer for Question 129
Answer: C (The RPI would be less than 2, both ferritin and serum iron would be decreased, and TIBC would be increased)
Explanation: Given a slow developing anemia in a younger female, iron deficiency due to blood loss related to heavy menstrual or irregular menstrual bleeding is most likely. The low MCV confirms a microcytic anemia. In iron deficiency anemia, there is underproduction of the red blood cells, which is indicated by the RPI (reticulocyte production index) of <2. As the body has a decreased amount of iron, both the serum iron and ferritin (i.e., the storage form of iron) would be decreased. Because the amount of iron in the body is decreased, the body has more capacity to bind iron, because no iron is available (i.e., the binding sites for iron are open and available for iron to deposit), and therefore the TIBC (total iron binding capacity) would be increased.
Question 130
A 43-year-old alcoholic male presents to an acute care clinic complaining of fatigue. A complete blood cell count is performed and reveals a hemoglobin of 8.3 g/dL and hematocrit of 24%. The white blood cell count and platelet count are also slightly lower than the reference range for the lab. The MCV is 120 fL. Additional laboratory testing reveals elevated concentrations of homocysteine and methylmalonic acid. A deficiency of which of the following nutrients would explain his condition?
A. Vitamin B12
B. Folate
C. Iron
D. Calcium
E. Copper
Answer for Question 130
Answer: A (vitamin B12)
Explanation: The patient has a megaloblastic anemia, characterized by a decreased concentration of hemoglobin and a markedly elevated MCV. Two causes of megaloblastic anemia are deficiency of folate or vitamin B12. A deficiency of either will result in elevated concentrations of homocysteine; however, a deficiency of B12 will also result in a deficiency of methylmalonic acid.