The commonest mode of inheritance of Von Willebrand’s disease :
First, I need to recall the inheritance patterns. Hemophilia A is X-linked recessive, right? But Von Willebrand's is different. I think it's more common and has different inheritance types. There are three types of Von Willebrand's disease: Type 1, 2, and 3. Type 1 is the mildest and most common. Now, what about their inheritance?
I remember that Type 1 and Type 3 have different inheritance patterns. Type 3 is autosomal recessive, which is rare. Type 2 is autosomal dominant but with variable expression. But Type 1 is the most common, and I think it's autosomal dominant. Wait, but sometimes there's a recessive form too? No, Type 1 is usually dominant. So the commonest mode is autosomal dominant.
Wait, let me check. Von Willebrand's disease is caused by mutations in the VWF gene on chromosome 12. The inheritance depends on the type. Type 1 is autosomal dominant with variable expressivity. Type 2 is also autosomal dominant, with different subtypes. Type 3 is autosomal recessive. Since Type 1 is the most prevalent form, the commonest inheritance would be autosomal dominant. So the correct answer should be autosomal dominant. The options probably have that as one of the choices. The other options might be X-linked recessive, autosomal recessive, or maybe another type. So the correct answer is autosomal dominant.
**Core Concept** Von Willebrand’s disease (vWD) is the most common inherited bleeding disorder, caused by quantitative or qualitative defects in von Willebrand factor (VWF), a protein essential for platelet adhesion and factor VIII stabilization. Its inheritance pattern varies by subtype.
**Why the Correct Answer is Right** The most common subtype, **Type 1 vWD** (80–85% of cases), follows **autosomal dominant inheritance**. It results from heterozygous mutations in the *VWF* gene on chromosome 12, leading to partial VWF deficiency. This pattern explains its high prevalence and variable expressivity, with mild to moderate bleeding symptoms.
**Why Each Wrong Option is Incorrect**
**Option A:** *X-linked recessive* is incorrect—vWD is autosomal, not X-linked.
**Option B:** *Autosomal recessive* applies to **Type 3 vWD** (rarest, severe form), but this accounts for <1% of cases.
**Option C:** *Mitochondrial inheritance* is irrelevant here—no mitochondrial mutations are involved in vWD.
**Clinical Pearl / High-Yield Fact** Remember: **Type 1 vWD is autosomal dominant (most common), Type 2 is autosomal dominant with variable expression, and Type 3 is autosomal recessive (most severe)**. Confusion with hemophilia A (X-linked) is common but critical for management.
**Correct Answer: B. Autosomal dominant**