**Question:** Lalita, a female pt. presents with pigmentation of the lips and oral mucosa and intestinal polyps. Her sister also gives the same history. Most probable diagnosis is

A. Addison's disease
B. Multiple endocrine neoplasia type 2
C. Peutz-Jeghers syndrome
D. Familial adenomatous polyposis (FAP)

**Correct Answer:** D. Familial adenomatous polyposis (FAP)

**Core Concept:**

Multiple endocrine neoplasia (MEN) syndromes, familial adenomatous polyposis (FAP), and Peutz-Jeghers syndrome are genetic disorders characterized by the development of polyps and tumors in various organs. Addison's disease is an autoimmune disorder affecting the adrenal glands and is not related to polyposis or mucosal pigmentation.

**Why the Correct Answer is Right:**

Familial adenomatous polyposis (FAP) is a genetic disorder characterized by the development of numerous adenomatous polyps in the colon, rectum, and other organs. The mucosal pigmentation and oral lesions are secondary to the chronic inflammation caused by these polyps, leading to mucosal changes. Intestinal polyps can also cause gastrointestinal bleeding, which is a part of Lalita's symptoms.

**Why Each Wrong Option is Incorrect:**

A. Addison's disease is an autoimmune disorder affecting the adrenal glands, not associated with polyposis or mucosal pigmentation.
B. Multiple endocrine neoplasia type 2 (MEN2) is characterized by medullary thyroid carcinoma, pheochromocytoma, and mucosal pigmentation, but not intestinal polyps.
C. Peutz-Jeghers syndrome is characterized by mucocutaneous pigmentation and gastrointestinal hamartomatous polyps, but it does not typically affect females.

**Clinical Pearl:**

Peutz-Jeghers syndrome is a rare autosomal dominant disorder caused by mutations in the LKB1 gene. It is characterized by mucocutaneous pigmentation and gastrointestinal hamartomatous polyps, which can lead to gastrointestinal bleeding and bowel obstruction. In contrast, FAP is an autosomal dominant disorder caused by mutations in the APC gene, affecting females. It is characterized by adenomatous polyps in the gastrointestinal tract, leading to gastrointestinal bleeding, megacolon, and an increased risk of colorectal cancer.

In conclusion, the correct answer (D) is chosen due to the specific characteristics of FAP, including the development of numerous adenomatous polyps in the gastrointestinal tract, leading to gastrointestinal bleeding and an increased risk of colorectal cancer. The other options (A, B, C) lack the specific features of FAP, such as gastrointestinal bleeding and the development of adenomatous polyps in females.