Table 3.

Syndrome Genetic Testing and Indications for Genetic Testing

Syndrome	Involved Gene(s)	Indication to perform genetic testing	Frequency of identifying a genetic mutation in an index case
Familial adenmoatous polyposis (FAP) and attenuated FAP (AFAP)	APC	≥10 colonic adenomas, ≥5 adenomas with suggestive family history	80% to 90%
Hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch syndrome	MLH1, MSH2, MSH6, PMS2	Positive Amsterdam criteria or Bethesda guidelines, see also text and Figure 1	50% to 70%
MYH gene associated polyposis (MAP)	MYH	Same as FAP and AFAP	MYH gene mutation found in 10% to 15% of FAP families not found to have APC mutations, and found in 10% to 40% of persons with 15 to 100 colorectal adenomas
Peutz-Jeghers syndrome (PJS)	STK11	Histologically typical gastrointestinal polyps or typical oral or facial pigmentation	90% to near 100%
Juvenile polyposis syndrome (JPS)	BMPR1A, SMAD4, ENG	≥3 juvenile polyps	About 20% of JPS is caused by BMPR1A mutations, about 20% by SMAD4 mutations, and ENG mutation families are rare
Cowden syndrome (CS)	PTEN	Typical skin findings or finding gastrointestinal juvenile polyps but not JPS, see Table 2	50% to 90%
Hereditary mixed polyposis syndrome (HMPS)	Candidate locus at 15q13–14; ?BMPR1A	Mixed histology colonic polyposis	N/A
Hyperplastic polyposis syndrome (HPS)	Unknown, rarely familial	> 20 colonic hyperplastic polyps, or ≥ larger hyperplastic polyps (≥1 cm)	N/A

NOTE: accuracy of mutation specific genetic testing for other family members, once a mutation has been identified in the index, case is near 100%