A 12-year-old boy presents with recurrent colicky abdominal pain and dark brown macules on his lower lip and buccal mucosa. His father had similar pigmentation and died of pancreatic cancer. The most likely gene mutation is:

• A APC
• B SMAD4
• C PTEN
• D STK11 ✓

Explanation

Peutz-Jeghers syndrome (PJS) is an autosomal dominant disorder caused by mutations in the STK11 (LKB1) tumor suppressor gene. It is characterized by mucocutaneous melanin macules, most commonly on the lips and buccal mucosa, and hamartomatous polyps in the gastrointestinal tract. The pigmentation often fades after puberty. Patients have an increased risk of gastrointestinal and extraintestinal malignancies. APC mutations cause familial adenomatous polyposis, PTEN causes Cowden syndrome, and SMAD4 causes juvenile polyposis syndrome.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.