In congenital dystrophic variety of epidermolysis bullosa, mutation is seen in the gene coiling for :
**Core Concept**
Epidermolysis bullosa (EB) is a group of genetic disorders characterized by skin fragility and blistering. The congenital dystrophic variety of EB is caused by mutations in genes encoding proteins essential for anchoring the epidermis to the dermis. Coiling of proteins is crucial for maintaining the integrity of the skin.
**Why the Correct Answer is Right**
In congenital dystrophic epidermolysis bullosa, mutations are seen in the gene coding for **collagen type VII**. This protein is secreted by keratinocytes and forms a coiled-coil structure that anchors the epidermis to the dermis through hemidesmosomes. The coiled-coil structure of collagen type VII provides tensile strength to the anchoring fibrils, which are essential for maintaining the integrity of the skin.
**Why Each Wrong Option is Incorrect**
* **Option A:** Not relevant to congenital dystrophic epidermolysis bullosa.
* **Option B:** Mutations in the gene coding for laminin 5 are associated with junctional epidermolysis bullosa, not congenital dystrophic epidermolysis bullosa.
* **Option C:** Not a known gene associated with epidermolysis bullosa.
**Clinical Pearl / High-Yield Fact**
Collagen type VII is a crucial protein in maintaining the integrity of the skin. Mutations in the gene coding for collagen type VII can lead to congenital dystrophic epidermolysis bullosa, a severe form of epidermolysis bullosa characterized by skin fragility and blistering.
**Correct Answer:** D.