The genetic defect responsible for PNH involves the PIGA gene. What is its primary role?

• Stabilization of spectrin and ankyrin

• Synthesis of glycosylphosphatidylinositol (GPI) anchor proteins

• Regulation of hemoglobin binding capacity

• Transport of iron across the RBC membrane

Which of the following CD markers are absent in PNH, leading to uncontrolled complement lysis?

• CD45 and CD34

• CD55 and CD59

• CD11b and CD16

• CD71 and CD235a

CD55 is also known as:

• Membrane inhibitor of reactive lysis (MIRL)

• Decay accelerating factor (DAF)

• Complement receptor 1 (CR1)

• Properdin factor

CD59 is also referred to as:

• Complement control protein

• Membrane inhibitor of reactive lysis (MIRL)

• Complement regulatory antigen

• Inhibitor of C3 convertase

Why are complement proteins particularly destructive to RBCs lacking CD55/CD59?

• They directly block ATP generation

• They coat the RBCs and induce MAC (membrane attack complex) formation

• They impair hemoglobin synthesis

• They fragment spectrin-actin complex

The term “paroxysmal” in PNH refers to:

• Hemolysis that occurs predominantly in the morning

• Sudden intermittent episodes of hemolysis

• Constant ongoing hemolysis regardless of time

• Complement activation only in febrile states

Hemoglobinuria in PNH is usually most evident in:

• Morning urine specimen

• 24-hour urine specimen

• Random spot urine

• Evening urine specimen

Which type of PNH exhibits complete absence of GPI-linked proteins?

• Type I

• Type II

• Type III

• Type IV

In PNH, flow cytometry quantifies the level of:

• Hemoglobin concentration in plasma

• Expression of CD55 and CD59 on RBCs and WBCs

• Complement levels in serum

• Osmotic fragility of spherocytes

A screening test for PNH that mixes whole blood with sugar water and checks for hemolysis is:

• Ham’s test

• Sucrose hemolysis test

• Sugar water test

• Eosin-5’-maleimide test