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Familial Adenomatous Polyposis : Introduction

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Introduction: Familial adenomatous polyposis (FAP) is the most common adenomatous polyposis syndrome. The patients develop hundreds to thousands of adenomatous polyps early in life (teens or 20s) with a 100% risk of developing into colorectal carcinoma. It includes the classic FAP as well as variant forms such as Gardner syndrome, Turcot syndrome, and attenuated FAP. In the classic form of FAP, the average age by which cancer develops is 39 years. There is an attenuated form of FAP in which polyp formation is delayed and the average age for colorectal cancer onset is 55 years.

Frequency: The incidence of FAP is reported to be between 1 in 7,000 to 1 in 22,000.

Inheritance Pattern: About 75% of FAP cases are inherited as an autosomal dominant disorder. The remaining 25% of patients with FAP have a negative family history and are de novo mutations.

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