Background/aims: To determine the carrier frequency of ABCA4 mutations in order to achieve an insight into the prevalence of autosomal recessive Stargardt disease (arSTGD) in Spanish population.
Methods: 133 arSTGD patients were analysed using the ABCR400 microarray and sequencing. Controls were analysed by two different strategies: 200 individuals were screened for the p.Arg1129Leu mutation by dHPLC and sequencing; whereas 78 individuals were tested for variants on the microarray and sequencing.
Results: For the 1st strategy in controls, the p.Arg1129Leu variant was found in two heterozygous individuals, which would suppose a carrier frequency for any variant of ~6.0% and a calculated arSTGD prevalence of 1:1000. For the 2nd strategy, carrier frequency was 6.4% and therefore, an estimated prevalence of the disease of 1:870.
Conclusion: Calculated prevalence of arSTGD, based on the ABCA4 carrier frequency, could be considerably higher than previous estimation. This discrepancy between observed (genotypic) and estimated (phenotypic) prevalence could be due to the existence of non-pathological or low penetrance alleles, which may result in late onset arSTGD or may be implicated in age-related macular degeneration (AMD). This situation should be regarded with especial care when genetic counselling is given and further follow-up of these patients should be recommended.