Familial polyposis coli: the spectrum of ocular and other extracolonic manifestations

Value of the congenital hypertrophy of the retinal pigment epithelium in the diagnosis of familial adenomatous polyposis

BACKGROUND

Several kinds of congenital hypertrophy of the retinal pigment epithelium (CHRPE) have been described in patients with familial adenomatous polyposis (FAP). This study aims to assess which properties of CHRPE better predict FAP and investigate whether a relationship exists between specific CHRPE characteristics and FAP variants.

METHODS

We examined 286 subjects, Group I--patients with FAP plus individuals "at risk"; n = 173; Group II--controls n = 113. Retinal lesions were classified in five types (A-E) and different characteristics (distribution, number, shape, size, pigmentation and site) were evaluated.

RESULTS

The most common lesions in affected subjects were types A-D (83.4%) whilst in the "at risk" and control groups were type E. Greater numbers of lesions and bilateral distribution occurred more frequently among affected subjects than in other participants (p < 0.001). Large lesions with mixed pigmentation were associated with polyposis (p > 0.5). Controls had solitary CHRPE lesions (3.5%) and types C and E lesions (23%). The cumulative sensitivities and specificities of CHRPE were 42 and 97%, respectively. CHRPE was most common among those with classical FAP, but no specific characteristic was associated with any particular FAP variant.

CONCLUSIONS

Pigmented fundal lesions are highly pleomorphic and represent the variable expression of a common genetic defect of growth regulation. No association was found between CHRPE characteristics and specific FAP variants.

Diagnostic value of fundus examination in familial adenomatous polyposis

BACKGROUND

Multiple, bilateral lesions of congenital hypertrophy of the retinal pigment epithelium (CHRPE) have been described in patients suffering from familial adenomatous polyposis (FAP) since 1980. This study aimed to determine a reliable diagnostic criterion, based on the size and number of retinal CHRPE lesions, allowing the screening of patient carriers of the gene responsible for FAP.

METHODS

32 control subjects and 144 patients belonging to 85 FAP families were studied, divided into 124 carriers of the genetic alteration and 20 non-carriers.

RESULTS

In carriers of the deleted gene, multiple, bilateral retinal lesions were consistently observed. Lesion situation, size, shape, and degree of pigmentation were variable however. A positive criterion for FAP was defined as the presence of at least four lesions whatever their size, or at least two lesions one of which is large. This criterion showed a high sensitivity (0.68) and a maximal specificity (1). Within each family, the retinal phenotypic expression was homogeneous. CHRPE lesions were observed in two thirds of the FAP families and absent from the remaining third.

CONCLUSION

By using this new positive diagnostic criterion, fundus examination allows early detection of those children carrying the gene responsible for FAP in families positive at ocular examination.

Multiple familial pilomatricomas: a cutaneous marker for Gardner syndrome?

A 40-year-old man and his 6-year-old only son had numerous, firm papulonodular lesions on their faces. Their medical histories were unremarkable and no family consanguinity was recorded. Surgical excision of several lesions was performed on each patient. All the lesions were solid tumors with the characteristic histopathologic features of pilomatricoma. A gastrointestinal radiologic and fibroscopic survey disclosed numerous adenomatous colonic polyps in the father. Additional studies revealed that he also had minor dental abnormalities, a small osteoma on the right mandible, and unilateral, ocular, pigmented retinal macules. The diagnosis of multiple adenomatous colonic polyposis was established only after the well-known association of pilomatricoma-like changes in epidermal cysts in patients with Gardner syndrome was considered. Possibly, multiple familial pilomatricomas could be considered a cutaneous marker of Gardner syndrome.

Genetic heterogeneity of congenital hypertrophy of the retinal pigment epithelium (CHRPE) in families with familial adenomatous polyposis

One hundred and eighteen subjects with familial adenomatous polyposis (FAP) and 80 of their relatives who were at low risk (< 0.01) of carrying the FAP gene were scored by one of us (BJ) or by colleagues to assess the frequency of congenital hypertrophy of the retinal pigment epithelium (CHRPE). A CHRPE is defined as an "oval pigmented lesion surrounded by depigmented halo". Seventy five (63.6%) of the FAP cases and one (1.2%) of their relatives had at least one CHRPE. There was no systematic difference in the number of CHRPEs in the left and right eyes so all analyses are based on total number of CHRPEs and the findings were highly correlated (p = 0.001 for a test of no correlation). There was also no evidence of any age effect in total number of CHRPEs in affected subjects. In 26 families there was more than one subject affected with FAP. There was a significant common family effect with respect to CHRPE expression for total number of CHRPEs with an F statistic of 1.73 (p = 0.02 for a test of no family aggregation) indicating that family members are more similar to each other than to affected subjects from other families. This may indicate that specific mutations play a role in determining the number of CHRPEs. Nine affected subjects had intra-abdominal desmoids, and in these the frequency of each of the types of CHRPE was no higher (in fact, slightly lower) than the average for affected subjects without desmoids, but this difference was not significant (p > 0.3).

Restriction of ocular fundus lesions to a specific subgroup of APC mutations in adenomatous polyposis coli patients

In humans, alteration of the tumor suppressor gene, APC, causes adenomatous polyposis coli, a condition causing predisposition to colorectal cancer. The syndrome inconsistently associates characteristic patches of congenital hypertrophy of the retinal pigment epithelium (CHRPE). Ocular examination revealed that patients expressing CHRPE tend to cluster within specific families. The exact APC mutation was identified in 42 unrelated patients. In all cases these mutations were predicted to lead to the synthesis of a truncated protein. The extent of CHRPE was found to be dependent on the position of the mutation along the coding sequence. CHRPE lesions are almost always absent if the mutation occurs before exon 9, but are systematically present if it occurs after this exon. Thus, the range of phenotypic expression observed among affected patients may result in part from different allelic manifestations of APC mutations.

Fundus changes associated with congenital hypertrophy of the retinal pigment epithelium

The clinical characteristics and follow-up changes of 64 patients with solitary congenital hypertrophy of the retinal pigment epithelium were studied. Thirty-five of the patients were followed up for one to 14 years with serial fundus photography. Progressive increase of the hypopigmented part of the lesion was observed in 29 of the 35 patients who were followed up (82.8%). An enlargement of the lesion was seen in 26 of the 35 patients (74.3%). Two additional changes, that is, pigmented areas adjacent to congenital hypertrophy of the retinal pigment epithelium and linear streaks of the pigment epithelium, were documented. Pathogenetic mechanisms for the development of these changes remain unknown.

Congenital hypertrophy of the retinal pigment epithelium and familial adenomatous polyposis

Congenital hypertrophy of the retinal pigment epithelium is a common eye sign in patients with familial adenomatous polyposis (FAP). FAP has autosomal dominant inheritance with virtually 100% risk of colonic malignancy in adult life. There may be other associated systemic abnormalities including extracolonic malignancy. Early detection of disease is desirable, but has in the past been reliant on regular endoscopic examination. The nature of congenital hypertrophy of the retinal pigment epithelium and its usefulness as a predictive marker of the disease are discussed.