An Rh -ve woman became pregnant with Rh +ve fetus. Within few days after bih, the infant developed jaundice, ascites, hepatomegaly and edema. The likely substance(s) deposited in skin and sclera in jaundice is/are given below. Which is the best possible answer?
**Core Concept**
The underlying principle being tested is the pathophysiology of hemolytic disease of the newborn (HDN), which occurs when there is an incompatibility between the blood types of the mother and the fetus, specifically regarding the Rh factor. This incompatibility leads to the production of antibodies by the mother's immune system against the fetus's red blood cells. **Hemolysis** of the fetus's red blood cells results in the release of **bilirubin**, leading to **jaundice**.
**Why the Correct Answer is Right**
In the context of HDN due to Rh incompatibility, the mother's immune system produces **IgG antibodies** against the Rh-positive red blood cells of the fetus. These antibodies cross the placenta and cause **hemolysis** of the fetal red blood cells, leading to an increase in **unconjugated bilirubin**. This form of bilirubin is lipid-soluble and can deposit in tissues, causing **jaundice**. The correct substance deposited in the skin and sclera in this condition is **unconjugated bilirubin**.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it does not specify the type of bilirubin involved in jaundice due to hemolytic disease of the newborn.
**Option B:** Incorrect as it is not directly related to the pathophysiology of HDN.
**Option C:** Incorrect because, although bilirubin is involved, the specific type and context are not accurately described.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that **unconjugated bilirubin** is the form that accumulates in the tissues and causes jaundice in hemolytic disease of the newborn. This is crucial for understanding the pathophysiology and clinical presentation of HDN.
**Correct Answer:** D. Bilirubin