104 Hematology
away from iron deficiency. Look for polychromatophilic stippling and the classic "ringed siderob-
last" in the bone marrow (know what it looks like). Sideroblastic anemia may be related to
myelodysplasia or future blood dyscrasia. Although probably you will not be asked about manage-
ment, treatment is supportive. In rare cases the anemia responds to pyridoxine. Do not give iron.
32. How do you recognize anemia of chronic disease?
First, look for the presence of a disease that causes chronic inflammation (e.g., rheumatoid
arthritis, lupus erythematosus, cancer, tuberculosis). The anemia is either normocytic or micro-
cytic. Serum iron is low, but so is total iron-binding capacity. Thus, the percent saturation may
be near normal. Serum ferritin is elevated (because ferritin is an acute-phase reactant, the level
should be increased). Treat the underlying disorder to correct the anemia. Do not give iron.
33. Describe the hallmarks of spherocytosis.
This normochromic, normocytic anemia is associated with spherocytes on peripheral smear,
positive family history (autosomal dominant), splenomegaly, positive osmotic fragility test, and
an increased mean corpuscular hemoglobin concentration (the only occasion on which this red
blood cell index is useful for the Step 2 exam). Treatment often involves splenectomy. Sphero-
cytes also may be seen in extravascular hemolysis, but the osmotic fragility test is normal.
34. Why do chronic renal disease patients develop anemia? How do you treat it?
All patients with chronic renal failure develop a normocytic, normochromic anemia with
decreased reticulocyte count due to decreased erythropoietin production. Give erythropoietin to
correct the anemia.
35. What clues point to a diagnosis of aplastic anemia?
Although aplastic anemia may be idiopathic, on the Step 2 exam watch for chemotherapy,
radiation, malignancy affecting the bone marrow (especially leukemias), benzene, and implicated
medications (e.g., chloramphenicol, carbamazepine, phenylbutazone, sulfa drugs, zidovudine,
gold). Decreased white blood cells and platelets accompany the anemia. Treat first by stopping
any possible causative medication; then try antithymocyte globulin, colony-stimulating factors
(such as erythropoietin, sargramostim, and filgrastim), or bone marrow transplant.
36. Define myelophthisic anemia. What clues on the peripheral smear suggest its presence?
Myelophthisic anemia is due to a space-occupying lesion in the bone marrow. The common
causes are malignant invasion that destroys bone marrow (most common) and myelodysplasia or
myelofibrosis. On the peripheral smear, look for marked anisocytosis (different size), poikilocy-
tosis (different shape), nucleated red blood cells, giant and/or bizarre-looking platelets, and
teardrop-shaped red blood cells. A bone marrow biopsy may reveal no cells ("dry tap" if the
marrow is fibrotic) or malignant-looking cells.
37. How do you recognize glucose-6-phosphatase deficiency on the USMLE?
This genetic disorder is X-linked recessive, affecting males. It is most common in blacks and
Mediterraneans. Look for sudden hemolysis or anemia after exposure to fava beans or certain
drugs (antimalarials, salicylates, sulfa drugs) or after infection. You may see Heinz bodies and
"bite cells" on peripheral smear. The diagnosis is made with a red blood cell enzyme assay, which
should not be done immediately after hemolysis because of the potential for a false-negative
result. All of the older red blood cells already have been destroyed, and the younger red blood
cells are not affected in most patients. Treat with avoidance of precipitating foods and medica-
tions; discontinue the triggering medication first.
38. Name some other causes of anemia.
• Endocrine failure (especially pituitary and thyroid; look for endocrine symptoms)
• Mechanical heart valves (hemolyzed red blood cells)
