Pterygium in an Isolated Population

Abstract

SUMMARYThe incidence of pterygium was studied in an isolated highly inbred fisher population. A clinical and hematological examination was performed and the blood chemistry was studied. Genealogical tables (pedigrees) were prepared for all probands and the degree of consanguinity in their parents stated. Of the total of 479 subjects studied by random sampling, 19 (4 per cent) had pterygium with a relatively high manifestation age. No linkage was detected between the genes for the blood group systems, serum groups etc. and the gene for pterygium. Increased capillary fragility was established in 10 probands. Capillary permeability was studied in 2 probands by the concentration in the anterior chamber of intravenously administrated fluorescein, and the test was found to be weakly pathological in one of them. The serum cholesterol level was elevated in 5 of the patients studied. Ophthalmological examination indicated the accumulation of degenerative eye diseases. Pingueculum showed a more pronounced development in 10 of the 17 subjects examined than in the rest of the population. The possibility of recessive transmission of the hereditary predisposition is discussed with reference to the high frequency of inbreeding and the accumulation of pterygium within the isolated population. According to the special frequency-raising peristasis conditions in an outer archipelago community and to the mendelian segregation rate, a not sex-linked, simple dominant gene, with low penetrance and no selective disadvantage for the pterygium seems to be the most plausible explanation. Because of the late manifestation age, pterygium was observed only in 2 generations. The expressiveness of the gene was unsteady and asymmetry of pterygium in the eyes of the probands is not uncommon.