Background: Familial adenomatous polyposis (FAP) is a hereditary disease characterized by more than 100 adenomas scattered in the large bowel and by various extracolonic manifestations. We proposed a) to establish the frequency of the disorder in Northern Italy, b) to describe the most relevant clinical findings, and c) in a subgroup of 21 patients (from 8 families), to evaluate the spectrum of mutations of the APC gene.
Methods and results: Patients with FAP diagnosed between 1961 and 1991 were referred to our Study Group from surgery and gastroenterology units of the region Emilia-Romagna. The incidence of FAP was in the order of 1 in 16,500, with about a third of patients being 'single' cases. Colorectal malignancies were present in 75.6% of symptomatic patients but absent in most (93.75%) of the asymptomatic family members ('call-up' individuals). Gastric, duodenal, and jejunal adenomas were found in 8.2%, 30.6% and 53.3% of the investigated patients, respectively. Congenital hypertrophy of the retinal pigment epithelium and occult jaw lesions were seen in 64.7% and 39.5% of FAP patients but only in 0.5% and 2.5% of a matched, by age and sex, control population. These two clinical markers had a specificity of 99% and 97%, although their sensitivity was 64% and 39%. Finally, mutations of the APC gene were detected in 6 families (16 affected individuals) of the 8 families (21 affected individuals) tested; no correlation could be found between genotype and phenotype.
Conclusions: This study confirms that early diagnosis is essential for an appropriate management of FAP patients, although this aim remains elusive in single cases. High-risk individuals are ideal candidates for APC gene mutation analysis, which should be offered to all first-degree relatives of affected patients.