PNH301 Test 2 2025 | Questions & Answers
with Complete Solution | Psychiatric
Nursing Guide
Question 1: Which cell type is primarily affected in paroxysmal nocturnal hemoglobinuria (PNH)?
A) T lymphocytes
B) B lymphocytes
C) Red blood cells
D) All blood cell lines
Correct Answer: D) All blood cell lines
Explanation: PNH is an acquired clonal disorder of hematopoietic stem cells lacking GPI-anchored
complement regulatory proteins, making erythrocytes, leukocytes, and platelets vulnerable to
complement attack.
Question 2: The underlying molecular defect in PNH involves mutation of which gene?
A) HBB
B) PIGA
C) BCR-ABL
D) JAK2
Correct Answer: B) PIGA
Explanation: Somatic mutation in the X-linked PIGA gene prevents synthesis of
glycosylphosphatidylinositol (GPI) anchors, leading to loss of CD55 and CD59 on blood cells.
Question 3: Which complement regulatory protein is absent on PNH erythrocytes and normally
accelerates decay of C3 convertase?
A) CD35
B) CD55 (DAF)
C) CD59 (MIRL)
,D) C1-inhibitor
Correct Answer: B) CD55 (DAF)
Explanation: CD55 (decay-accelerating factor) destabilizes C3/C5 convertases; its absence allows
unchecked complement amplification and hemolysis.
Question 4: The classic dark morning urine in PNH is caused by:
A) Myoglobinuria
B) Bilirubinuria
C) Hemoglobinuria from intravascular hemolysis
D) Porphyrinuria
Correct Answer: C) Hemoglobinuria from intravascular hemolysis
Explanation: Complement-mediated lysis of RBCs at night (mild hypoventilation-induced acidosis
activates complement) releases free hemoglobin filtered by kidneys.
Question 5: Which test is the gold standard for diagnosing PNH today?
A) Ham test
B) Sucrose lysis test
C) Flow cytometry for GPI-anchored proteins
D) Direct antiglobulin test
Correct Answer: C) Flow cytometry for GPI-anchored proteins
Explanation: High-sensitivity flow cytometry detecting absence of CD55/CD59 or FLAER failure on
granulocytes/RBCs is now diagnostic standard.
Question 6: What percentage of GPI-deficient granulocytes is generally considered diagnostic for
PNH?
A) 0.1%
B) 1%
C) 10%
D) 50%
Correct Answer: B) 1%
, Explanation: ≥1% GPI-deficient cells in any lineage is accepted as significant clone; smaller
percentages may be seen in marrow stress but not true PNH.
Question 7: Which thrombotic site is most characteristic for PNH?
A) Deep vein thrombosis
B) Portal vein thrombosis
C) Budd-Chiari syndrome (hepatic vein)
D) Pulmonary embolus
Correct Answer: C) Budd-Chiari syndrome (hepatic vein)
Explanation: intra-abdominal veins, especially hepatic veins, are disproportionately affected due to
complement activation on platelets in the splanchnic circulation.
Question 8: The term "paroxysmal nocturnal" refers to:
A) Night-time fever spikes
B) Intermittent hemolysis exacerbated during sleep
C) Seizures at night
D) Nocturnal thrombosis
Correct Answer: B) Intermittent hemolysis exacerbated during sleep
Explanation: Mild nocturnal respiratory acidosis activates complement, causing cyclic hemolysis
noted by dark morning urine.
Question 9: Which hemolytic marker is typically markedly elevated in active PNH?
A) Haptoglobin
B) Reticulocyte count
C) Iron saturation
D) Ferritin
Correct Answer: B) Reticulocyte count
Explanation: Chronic intravascular hemolysis stimulates erythropoiesis; reticulocytes often
>100-200 × 10⁹/L.
with Complete Solution | Psychiatric
Nursing Guide
Question 1: Which cell type is primarily affected in paroxysmal nocturnal hemoglobinuria (PNH)?
A) T lymphocytes
B) B lymphocytes
C) Red blood cells
D) All blood cell lines
Correct Answer: D) All blood cell lines
Explanation: PNH is an acquired clonal disorder of hematopoietic stem cells lacking GPI-anchored
complement regulatory proteins, making erythrocytes, leukocytes, and platelets vulnerable to
complement attack.
Question 2: The underlying molecular defect in PNH involves mutation of which gene?
A) HBB
B) PIGA
C) BCR-ABL
D) JAK2
Correct Answer: B) PIGA
Explanation: Somatic mutation in the X-linked PIGA gene prevents synthesis of
glycosylphosphatidylinositol (GPI) anchors, leading to loss of CD55 and CD59 on blood cells.
Question 3: Which complement regulatory protein is absent on PNH erythrocytes and normally
accelerates decay of C3 convertase?
A) CD35
B) CD55 (DAF)
C) CD59 (MIRL)
,D) C1-inhibitor
Correct Answer: B) CD55 (DAF)
Explanation: CD55 (decay-accelerating factor) destabilizes C3/C5 convertases; its absence allows
unchecked complement amplification and hemolysis.
Question 4: The classic dark morning urine in PNH is caused by:
A) Myoglobinuria
B) Bilirubinuria
C) Hemoglobinuria from intravascular hemolysis
D) Porphyrinuria
Correct Answer: C) Hemoglobinuria from intravascular hemolysis
Explanation: Complement-mediated lysis of RBCs at night (mild hypoventilation-induced acidosis
activates complement) releases free hemoglobin filtered by kidneys.
Question 5: Which test is the gold standard for diagnosing PNH today?
A) Ham test
B) Sucrose lysis test
C) Flow cytometry for GPI-anchored proteins
D) Direct antiglobulin test
Correct Answer: C) Flow cytometry for GPI-anchored proteins
Explanation: High-sensitivity flow cytometry detecting absence of CD55/CD59 or FLAER failure on
granulocytes/RBCs is now diagnostic standard.
Question 6: What percentage of GPI-deficient granulocytes is generally considered diagnostic for
PNH?
A) 0.1%
B) 1%
C) 10%
D) 50%
Correct Answer: B) 1%
, Explanation: ≥1% GPI-deficient cells in any lineage is accepted as significant clone; smaller
percentages may be seen in marrow stress but not true PNH.
Question 7: Which thrombotic site is most characteristic for PNH?
A) Deep vein thrombosis
B) Portal vein thrombosis
C) Budd-Chiari syndrome (hepatic vein)
D) Pulmonary embolus
Correct Answer: C) Budd-Chiari syndrome (hepatic vein)
Explanation: intra-abdominal veins, especially hepatic veins, are disproportionately affected due to
complement activation on platelets in the splanchnic circulation.
Question 8: The term "paroxysmal nocturnal" refers to:
A) Night-time fever spikes
B) Intermittent hemolysis exacerbated during sleep
C) Seizures at night
D) Nocturnal thrombosis
Correct Answer: B) Intermittent hemolysis exacerbated during sleep
Explanation: Mild nocturnal respiratory acidosis activates complement, causing cyclic hemolysis
noted by dark morning urine.
Question 9: Which hemolytic marker is typically markedly elevated in active PNH?
A) Haptoglobin
B) Reticulocyte count
C) Iron saturation
D) Ferritin
Correct Answer: B) Reticulocyte count
Explanation: Chronic intravascular hemolysis stimulates erythropoiesis; reticulocytes often
>100-200 × 10⁹/L.
