Purpose:
To examine the prevalence, genetic characteristics and related epidemiological factors in Danish children with generalized retinal dystrophy.
Methods:
The Danish registry for the Blind and Partially Sighted Children holds information on all Danish visually impaired children (age 0-17). Among registered children, the primary diagnosis of generalized retinal dystrophy was assessed by chart review, including fundus photographs and electroretinography. Annual numbers of live-born children in Denmark were retrieved from Statistics Denmark.
Results:
Of the 1,204,235 Danish children aged 0-17 years on October 1, 2011, 2012 children were registered as visual impaired. Of these, 153 cases were attributed to generalized retinal dystrophy, corresponding to a prevalence of 13 per 100,000 children, the age-specific prevalence increasing prominently with increasing age. Forty-three percent of the cases were syndromic, the remaining 57% being isolated cases. Among hereditary patterns, autosomal recessive was the most common, with 99 cases (66%). Forty-four percent of patients with classic isolated retinitis pigmentosa were simplex cases, with an excess of males (69%), indicating the presence of unrecognized x-linked cases. The prevalence of Leber's congenital amaurosis, Usher syndrome and Bardet-Biedl syndrome was twice that reported by Rosenberg in 1988. Forty-six percent of patients with the latter three diagnosis were offspring of recent immigrants from the Middle East with documented consanguinity in 75% of the cases, which may explain some of the observed increase in prevalence. A molecular genetic diagnosis had been made in 42% of the cases, 3% had ambiguous findings and 55% of the cases had not undergone molecular genetic analysis.
Conclusions:
This epidemiological survey demonstrates that the prevalence of generalized retinal dystrophy in Danish children is 13 per 100,000. Many such dystrophies are the subject of clinical intervention trials, but in more than half of the 153 prevalent cases the molecular diagnostic characterization is insufficient to enable selection of candidates for therapeutic trial participation.This emphasizes the requirement for further genetic studies.
Keywords: retinal degenerations: hereditary • clinical (human) or epidemiologic studies: prevalence/incidence • degenerations/dystrophies