Peutz-Jeghers syndrome features and gene.

• A. STK11 gene
• B. MSH2
• C. APC
• D. BRCA1

Answer: (A)

Peutz-Jeghers is defined by mucocutaneous pigmented macules around the lips and oral mucosa, together with hamartomatous polyps in the gastrointestinal tract, and a markedly increased lifetime cancer risk. It is caused by mutations in a tumor suppressor gene called STK11 (also known as LKB1). Loss of function in STK11 disrupts cellular growth control and polarity through pathways like AMPK, leading to the characteristic polyps and pigment changes. This condition is inherited in an autosomal dominant pattern with variable expression.

The other genes listed correspond to different hereditary cancer syndromes: MSH2 is linked to Lynch (hereditary nonpolyposis colorectal cancer) and mismatch repair defects; APC is associated with familial adenomatous polyposis and many colorectal adenomas; BRCA1 is linked to inherited breast and ovarian cancer risk.