MLT GlobeHematology: RBC indices & anemias – page 7
138 Hematology MCQs on RBC indices & anemias with answers and explanations.
An impedance analyzer reports low RBC count, high MCV and MCHC above 37 g/dL; values normalize after warming the sample to 37 °C. What is the cause?
Cold autoantibodies make red cells clump, so doublets are counted as single large cells: RBC falls, MCV and MCHC rise. Warming disperses the agglutinates. Lipemia raises Hb and MCHC but not MCV.
Deficiency of which vitamin has been associated with red cell aplasia (reduced erythroid precursors) in the marrow?
Riboflavin deficiency can cause a normocytic anemia with reticulocytopenia and erythroid hypoplasia. Vitamin K deficiency causes bleeding, not red cell aplasia.
Which drug is NOT used in managing sideroblastic anemia?
Pyridoxine helps some inherited forms, desferrioxamine treats iron overload, and androgens have been used to stimulate erythropoiesis. Hydroxyurea suppresses the marrow.
Which drug is classically associated with warm autoantibody production and a positive DAT, sometimes with hemolysis?
Methyldopa induces true red cell autoantibodies. Penicillin and quinidine cause hemolysis by other immune mechanisms; lithium is not a recognized cause.
The normal red cell mass (volume) in an adult man is approximately:
Red cell mass in men is about 25–35 mL/kg (women 20–30 mL/kg). Plasma volume is about 40–50 mL/kg; mL/L is the wrong unit.
In a man, above what hematocrit can an absolute increase in red cell mass be assumed without isotope studies?
British guidelines accept a hematocrit above 0.60 in men (0.56 in women) as always indicating raised red cell mass. Lower elevations may reflect reduced plasma volume.
A patient with chronic inflammation is also anemic. Which result best suggests coexisting iron deficiency?
Soluble transferrin receptor rises when erythroid cells lack iron but is not an acute-phase reactant, so it stays normal in pure anemia of chronic disease. Ferritin rises with inflammation and can hide iron deficiency.
Reticulocyte hemoglobin content (CHr or Ret-He) is useful because it reflects:
Reticulocytes circulate for only 1–2 days, so their hemoglobin content shows current iron supply to the marrow. It falls early in iron deficiency and rises within days of effective iron therapy.
A patient has a reticulocyte count of 6% and a hematocrit of 25%. Using a maturation (shift) factor of 2.0 and normal Hct of 45%, what is the reticulocyte production index (RPI)?
Corrected retic = 6 × 25/45 = 3.3%; RPI = 3.3 ÷ 2.0 = 1.7. The shift factor corrects for early release of stress reticulocytes that circulate longer.
A child with short stature, abnormal thumbs and progressive pancytopenia is investigated. Which test confirms the most likely diagnosis?
Fanconi anemia is an inherited DNA-repair defect causing marrow failure and skeletal abnormalities. Its lymphocytes show greatly increased chromosome breakage when exposed to DNA cross-linking agents.
An infant has severe macrocytic anemia with very low reticulocytes, normal white cells and platelets, and raised red cell adenosine deaminase. The most likely diagnosis is:
Diamond-Blackfan anemia is a congenital pure red cell aplasia presenting in infancy, often macrocytic, with raised erythrocyte ADA. Transient erythroblastopenia occurs in older children, is normocytic and has normal ADA.
Ring sideroblasts are defined on a Prussian blue-stained marrow as erythroblasts with:
ICSH/WHO define a ring sideroblast as an erythroblast with ≥5 siderotic granules covering at least a third of the nuclear circumference. These granules are iron-loaded mitochondria.
A child of consanguineous parents has microcytic anemia that does not respond to oral iron. Transferrin saturation is very low and hepcidin is inappropriately normal to high. Which gene defect is most likely?
TMPRSS6 encodes matriptase-2, which normally suppresses hepcidin. Its loss keeps hepcidin high and blocks iron absorption (iron-refractory iron deficiency anemia). HFE mutations cause low hepcidin and iron overload.
A young man has microcytic anemia with ring sideroblasts in the marrow. His maternal uncle had the same disorder, and his Hb improves with pyridoxine. Which enzyme is most likely defective?
X-linked sideroblastic anemia is caused by ALAS2 mutations; pyridoxal phosphate is its cofactor, so some cases respond to pyridoxine. Ferrochelatase defects cause erythropoietic protoporphyria.
In pernicious anemia, destruction of gastric parietal cells typically causes which additional laboratory finding?
Autoimmune gastritis causes achlorhydria; without acid feedback, G cells release more gastrin, so serum gastrin is high. Methylmalonic acid is raised, not low, in B12 deficiency.
A healthy 3-year-old has Hb 6.0 g/dL (60 g/L), reticulocytes 0.1%, normal MCV and normal WBC and platelets after a viral illness. HbF and red cell adenosine deaminase are normal. The most likely diagnosis is:
Transient erythroblastopenia occurs at 1–4 years, is normocytic, has normal HbF and eADA, and recovers in weeks. Diamond-Blackfan anemia presents in infancy with macrocytosis and raised HbF and eADA.
Two years after gastric bypass surgery, a patient has anemia and neutropenia. The marrow shows vacuoles in erythroid and myeloid precursors and some ring sideroblasts. B12 and folate are normal. The most likely cause is:
Copper deficiency, common after bariatric surgery or with zinc excess, causes anemia, neutropenia, precursor vacuoles and ring sideroblasts, mimicking myelodysplasia. It reverses with copper replacement. Iron deficiency does not cause neutropenia with vacuolated precursors.
A 60-year-old has isolated severe normocytic anemia, reticulocytes near 0%, and a marrow with almost no erythroid precursors but normal myeloid and megakaryocytic cells. CT shows an anterior mediastinal mass. The likely diagnosis is:
Pure red cell aplasia affects only the erythroid line and is classically associated with thymoma. Aplastic anemia reduces all three cell lines.