**Core Concept**
The Schwaz sign, also known as the "Schwartz sign," is a clinical indicator of a specific condition. It is a cutaneous manifestation of a deeper pathological process. The Schwaz sign is characterized by a bluish discoloration of the skin in a specific location.

**Why the Correct Answer is Right**
The Schwaz sign is seen in patients with a Meckel's diverticulum, which is a congenital diverticulum of the small intestine. The diverticulum contains ectopic gastric mucosa, which secretes acid and leads to inflammation and subsequent scarring of the surrounding tissue. The bluish discoloration of the skin, known as the "Schwartz sign," is due to the presence of ectopic gastric mucosa in the periumbilical region. This is because the ectopic gastric mucosa is in close proximity to the umbilicus, causing the characteristic discoloration.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the Schwartz sign is not associated with appendicitis, which presents with right lower quadrant pain and tenderness.
**Option B:** This option is incorrect because the Schwartz sign is not a characteristic feature of intussusception, which presents with abdominal pain, vomiting, and bloody stools.
**Option C:** This option is incorrect because the Schwartz sign is not associated with a Meckel's diverticulum without ectopic gastric mucosa.

**Clinical Pearl / High-Yield Fact**
The Schwartz sign is a classic exam question and is often tested in medical exams. It's essential to remember that the sign is associated with Meckel's diverticulum and ectopic gastric mucosa.

**Correct Answer: C. Meckel's diverticulum**