**Question:** The commonest mode of inheritance of von Willebrand's disease:

A. Autosomal Dominant
B. Autosomal Recessive
C. X-linked Dominant
D. X-linked Recessive

**Correct Answer:** .

**Core Concept:**
Von Willebrand's disease is a bleeding disorder that affects the body's ability to clot blood properly due to a deficiency or dysfunction in von Willebrand factor (vWF), a protein involved in platelet adhesion and clot formation. The condition can be inherited through different modes of inheritance depending on the affected gene and the mode of inheritance.

**Why the Correct Answer is Right:**
Von Willebrand's disease can have different modes of inheritance based on the involved gene. In the case of von Willebrand factor (vWF) deficiency, the condition is most commonly inherited through an **Autosomal Dominant** mode of inheritance. This means that one copy of the mutated gene from either parent is sufficient for the affected individual to have the disease.

**Why Each Wrong Option is Incorrect:**

A. Autosomal Recessive (vWF deficiency): The inheritance of a bleeding disorder through the **Autosomal Recessive** mode requires the affected individual to inherit a defective gene from both parents to manifest the disease. This is not the case for von Willebrand's disease in the context of vWF deficiency.

B. X-linked Dominant (vWF deficiency): A **X-linked Dominant** mode of inheritance would mean the disease is associated with the X chromosome. However, von Willebrand's disease due to vWF deficiency does not follow this pattern, as it is more commonly inherited through the autosomal dominant mode.

C. X-linked Recessive (vWF deficiency): In the case of an **X-linked Recessive** inheritance, the disease would affect both males and females. However, von Willebrand's disease due to vWF deficiency is more likely to affect individuals with an autosomal dominant inheritance pattern.

**Clinical Pearl:**

The concept of inheritance patterns is essential for understanding the mode by which genetic disorders like von Willebrand's disease are passed down through families. Familiarizing oneself with the different modes of inheritance, such as autosomal dominant and recessive, can help predict the likelihood of an individual developing the condition based on their family history, allowing for appropriate genetic counseling and management strategies.