mdali007
Credits:
5763
My Scrapbook
|
|
04.13.05 (3 years ago)
#2
|
|
The correct answer is E.
The laboratory values indicate that there is microcytic anemia. This form of anemia is associated with decreased mean cell volume of erythrocytes (microcytosis). By itself, microcytic anemia can be due to a number of factors, including iron deficiency and disorders of globin synthesis. When anemia is caused by iron deficiency, serum levels of iron and serum ferritin are decreased, whereas transferrin (plasma protein acting as iron carrier) is increased. Thus, this case is due to iron deficiency. Which of the above conditions may lead to iron deficiency? Uterine leiomyomas. These tumors arise from the smooth muscle of the uterus and often manifest with pain and abundant blood loss during menstruation. Any chronic blood loss leads to depletion of reserve iron and then to decreased synthesis of hemoglobin, ie, anemia. Maturation of erythrocytes is relatively unimpaired, but reduced synthesis of hemoglobin leads to smaller (microcytic) and paler (hypochromic) red blood cells. Remember that in Western countries, chronic blood loss is the most common cause of iron deficiency anemia.
ß-Thalassemia is due to mutations leading to a complete block or reduction in the synthesis of the ß-globin chain. ß-Thalassemia minor (choice A) is the clinical picture in patients heterozygous for the ß+ or ß0 gene. They are usually asymptomatic, but their blood smear shows variable degrees of hypochromasia and microcytosis. This condition must be distinguished from iron deficiency anemia. Accumulation of iron in ß-thalassemia minor leads to normal or increased plasma iron and ferritin, and reduced transferrin.
Chloramphenicol toxicity (choice B) may result in severe aplastic anemia. In this case, inability of the bone marrow to produce erythrocytes manifests with a reduced number of circulating erythrocytes, which are normochromic and normocytic. The most common causes of aplastic anemia are drugs.
Chronic autoimmune gastritis (choice C) is due to autoimmune destruction of the gastric mucosa. Autoantibodies blocking the binding between vitamin B12 and intrinsic factor are present in 75% of these cases. Impaired vitamin B12 absorption leads to megaloblastic anemia. Since vitamin B12 is an indispensable cofactor for DNA synthesis, defective cellular maturation and division occur, with abnormally large erythroid precursors and circulating erythrocytes that have a mean corpuscular volume up to 120 μm3. Circulating neutrophils are larger than normal and hypersegmented.
Many chronic diseases, including rheumatoid arthritis (choice D), may cause a form of anemia due to defective utilization of iron. This is referred to as anemia of chronic disease, and it may mimic iron deficiency anemia. However, anemia of chronic disease is associated with increased iron stores, reflected by elevated serum ferritin, reduced transferrin, and increased iron deposits in the bone marrow.
|
|
|
Topic Tags: 
