Which of the following is not seen in Hereditary Spherocytosis
**Core Concept**
Hereditary Spherocytosis (HS) is a genetic disorder characterized by the production of abnormal, sphere-shaped red blood cells (spherocytes) due to mutations in genes encoding proteins of the red blood cell membrane. This leads to premature red blood cell destruction (hemolysis) and anemia.
**Why the Correct Answer is Right**
Hereditary Spherocytosis is typically associated with a positive direct Coombs test (also known as direct antiglobulin test), which detects antibodies or complement proteins attached to the surface of red blood cells. This is due to the exposure of cryptic antigens on the spherocytic red blood cells. Additionally, HS often presents with jaundice, splenomegaly, and a family history of similar symptoms.
**Why Each Wrong Option is Incorrect**
**Option A:** Anisocytosis (unequal size of red blood cells) is a characteristic feature of Hereditary Spherocytosis, as the spherocytes are smaller than normal red blood cells.
**Option B:** Elevated indirect bilirubin levels are common in HS due to the breakdown of red blood cells, leading to jaundice.
**Option C:** The presence of spherocytes on peripheral blood smear is a hallmark diagnostic feature of HS.
**Clinical Pearl / High-Yield Fact**
Hereditary Spherocytosis can be caused by mutations in genes encoding proteins of the red blood cell membrane, including spectrin, ankyrin, protein 4.2, and band 3. This is an important consideration for patients with unexplained hemolytic anemia.
**Correct Answer: D.**