Epidemiology and genetics of primary congenital glaucoma in Slovakia. Description of a form of primary congenital glaucoma in gypsies with autosomal-recessive inheritance and complete penetrance.

This study includes all registered cases of PCG in the whole of Slovakia since 1950. Whenever possible the diagnosis was confirmed and a genealogical investigation was made. The patients were assigned to one of two groups depending on their ethnic origin - Gypsy or non-Gypsy. There were 118 Gypsy patients from 45 families (later reduced to 41 families) and 87 non-Gypsy patients from 81 families. Results from the Gypsy population can be summarised as follows: (1) Exceptionally high prevalence (1/2,120) and incidence (1/1,250) of PCG. (2) Sex ratio of 1:1. (3) High probability of autosomal-recessive inheritance based on results of segregation analysis (a priori method of Finney and Weinberg proband method). (4) Results of segregation analysis point to complete gene penetrance. (5) There was bilateral occurrence in all Gypsies. (6) The disease could already be diagnosed at birth in 82% of the patients. This shows that in the majority of cases the disease begins prenatally. (7) Clinical investigations indicated a more severe course and worse prognosis than in non-Gypsies. (8) The disease was familial in 85% of the PCG patients, i.e. only 15% of the cases were the only one in the family. (9) The proportion of kinship marriages among the parents of patients was 45%. (10) Values of 2.8% for the gene frequency and 5.4% for heterozygote frequency were established. (11) Relative reproductive fitness was estimated to be 0.26. (12) Selection coefficient was 0.74. (13) Inbreeding coefficient of patients from kinship marriages was 0.0203, for all patients together 0.0091. (14) The high incidence of the glaucoma gene can best be explained by genetic drift (founder effect). (15) Special measures to ensure early diagnosis and treatment would be justified on these grounds. The characteristics of PCG in the non-Gypsy population are comparable to those in published reports. (a) The prevalence (1/51,000) and the incidence (1/22,200) in the non-Gypsy population of Slovakia are slightly higher than, but still comparable to, those in the literature. (b) The sex ratio was significantly shifted towards the male side, being 1.55:1 (60.9% males). (c) The most common age at diagnosis was 6 months. The distribution of the ages at diagnosis is in accordance with that in the literature. (d) Bilateral PCG was present in 73% of the patients, corresponding to findings in other populations. (e) The proportion familial: sporadic (12:88) was similar to data in recent publications. (f) Kinship marriages were found in the parents of 5.9% of the patients.(ABSTRACT TRUNCATED AT 400 WORDS)