A 39-year-old woman is evaluated for severe left hip pain after twisting her leg. She has bony deformities of the lower extremities with limited mobility. The patient had a history of precocious pubey, hypehyroidism, which was managed by radioiodine therapy. Physical examination shows large, hyperpigmented-macules with irregular borders located on the left shoulder, left side of neck and left buttock. Which of the following gene is involved in this condition?

**Core Concept**
The patient's presentation of precocious puberty, hyperthyroidism, and bony deformities with limited mobility suggests a genetic disorder affecting multiple systems. This condition is associated with mutations in a gene responsible for the production of a hormone that regulates growth and development.

**Why the Correct Answer is Right**
The patient's symptoms are characteristic of McCune-Albright syndrome (MAS), a rare genetic disorder caused by mutations in the GNAS gene. The GNAS gene encodes for the stimulatory G protein subunit (Gsα), which is involved in the signaling pathway of various hormones, including thyroid-stimulating hormone (TSH) and growth hormone (GH). Mutations in the GNAS gene lead to constitutive activation of these pathways, resulting in precocious puberty, hyperthyroidism, and bony deformities due to fibrous dysplasia.

**Why Each Wrong Option is Incorrect**
* **Option A:** The MEN1 gene is associated with Multiple Endocrine Neoplasia type 1 (MEN1), a different genetic disorder that affects the parathyroid glands, pancreas, and pituitary gland.
* **Option B:** The FHH gene is associated with Familial Hypocalciuric Hypercalcemia (FHH), a genetic disorder that affects calcium regulation in the body.
* **Option C:** The RET gene is associated with Multiple Endocrine Neoplasia type 2 (MEN2), a genetic disorder that affects the thyroid gland, adrenal gland, and parathyroid gland.

**Clinical Pearl / High-Yield Fact**
McCune-Albright syndrome is a rare genetic disorder characterized by a triad of precocious puberty, hyperthyroidism, and fibrous dysplasia. The condition is caused by mutations in the GNAS gene, which affects the production of stimulatory G protein subunits.

**Correct Answer:** C.

✓ Correct Answer: A. GNAS