MUTYH-associated polyposis

Genetics

• Autosomal recessive
• Germline mutation of both alleles of the MUTYH gene, on chromosome 1
• Carriers are found about 1% of unselected individuals

Indications for testing

• >20 lifetime adenomas
• Younger age of onset adenomas or CRC (40-50yo)
• Siblings or children of MUTYH mutation carriers

Phenotype

• Mimics attenuated FAP
  • Mostly adenomas, can also get serrated adenomas
  • Rectal cancer uncommon
  • Lifetime risk of colon cancer 86% without screening
• Duodenal polyposis (20%)
• Gastric fundic polyps (rare)

Screening

• Colonoscopy 1-2 yearly
• Duodenoscopy starting at age 30, every 3-5 years

Surgery

• Subtotal colectomy - if endoscopic management fails, or CRC develops