Attenuated FAP 

About 8% of the families with FAP have an attenuated version of disease (called AFAP). 
AFAP is caused by hereditary mutations in the same APC gene as FAP, but the two affect different parts of the gene.

AFAP patients have much fewer bowel adenomas/polyps than those affected by FAP (less than 100, on average about 30, while FAP patients have hundreds or thousands). 

Contrary to FAP too, the AFAP polyps tend to appear on the right ascendant side of the colon, and as result should be preferentially monitored by colonoscopy. 

Due to their reduced number of polyps when compared with FAP patients, those with AFAP have less risk of cancer and later onset of both polyps and disease – at 45 and 66 years of age respectively.