**Core Concept:** Kinky hair disease is a genetic disorder characterized by short, white, and stubby hair, growth retardation, and premature brain degeneration, leading to death by the age of 2 years. This condition is caused by mutations in the "LMBR1" gene, which encodes a protein involved in hair follicle development.

**Why the Correct Answer is Right:** The correct mode of inheritance in this scenario is **Recessive Autosomal (A)**. This is because the disease is caused by a mutation in a single gene with two alleles, and both copies of the gene must be defective for an individual to be affected. In this case, the affected individuals (Mrs. A's sisters and her mother's brother) inherited the defective gene from their parents, who were carriers of the disease.

**Why Each Wrong Option is Incorrect:**

**A.** Dominant Autosomal (A): This mode of inheritance would mean that only one affected individual would be needed in the family, which is not the case here.

**B.** X-linked Recessive (XR): Dominantly inherited X-linked disorders are typically characterized by affected females being carriers and males being affected. Since both Mrs. A's sisters and her mother's brother are affected, XR is incorrect.

**C.** Autosomal Recessive (AR): As explained above, the family history does not support an autosomal dominant inheritance pattern.

**D.** X-linked Dominant (XD): Similar to option B, XD would imply affected females being carriers and males being affected, which doesn't apply to the provided family history.

**Clinical Pearl:** Family history plays a crucial role in determining the mode of inheritance in genetic disorders. In this case, the affected individuals' siblings and their mother's brother inherited the disease from their parents, who were carriers of the disease. Inheritance patterns can be complex, but understanding them is essential for clinical decision-making and genetic counseling.