The Correct Answer is C: Erythroblastosis Fetalis
Erythroblastosis fetalis (also known as hemolytic disease of the fetus and newborn, HDFN) is the only example of hemolytic anemia among the listed options. This condition occurs when maternal IgG antibodies cross the placenta and bind to paternally-derived antigens on fetal red blood cells, leading to their destruction through phagocytosis by macrophages, primarily in the spleen 1.
Why the Other Options Are Incorrect
Pernicious Anemia (Option A)
- This is not a hemolytic anemia
- It is a megaloblastic anemia caused by vitamin B12 deficiency due to lack of intrinsic factor
- Results in impaired DNA synthesis and abnormal red cell maturation, not red cell destruction
Hemophilia (Option B)
- This is not an anemia at all
- It is a bleeding disorder caused by deficiency of clotting factors (Factor VIII in Hemophilia A, Factor IX in Hemophilia B) 2
- While severe bleeding can lead to hemorrhagic anemia, hemophilia itself is a coagulation disorder, not a hemolytic process
Von Willebrand Disease (Option D)
- This is not an anemia
- It is an inherited bleeding disorder caused by deficiency or dysfunction of von Willebrand factor 2
- Like hemophilia, it affects hemostasis, not red blood cell survival
Understanding Erythroblastosis Fetalis as Hemolytic Anemia
The pathophysiology clearly demonstrates hemolysis 1:
Mechanism: Maternal IgG antibodies coat fetal red blood cells → Fc receptors on macrophages recognize these antibody-coated cells → phagocytosis occurs → red cell destruction (hemolysis)
Common antibodies involved: Anti-D (most common), anti-Kell, anti-Duffy, and other Rh system antibodies 1
Clinical consequences:
- Fetal anemia from red cell destruction
- Unconjugated hyperbilirubinemia from hemoglobin breakdown
- Potential hydrops fetalis from high-output cardiac failure
- Risk of stillbirth or neonatal death if untreated 1
This is a classic example of immune-mediated hemolytic anemia occurring in the alloimmune setting, where the immune system of one individual (the mother) produces antibodies against the red cells of another (the fetus) 3, 4.