Possible protective role of the ABCA4 gene c.1268A>G missense variant in Stargardt disease and syndromic retinitis pigmentosa in a Sicilian family: Preliminary data

In the wide horizon of ophthalmologically rare diseases among retinitis pigmentosa forms, Stargardt disease has gradually assumed a significant role due to its heterogeneity. In the present study, we aimed to support one of two opposite hypotheses concerning the causative or protective role of heterozygous c.1268A>G missense variant of the ABCA4 gene in Stargardt disease and in syndromic retinitis pigmentosa. This study was based on a family consisting of three members: proband, age 54, with high myopia, myopic chorioretinitis and retinal dystrophy; wife, age 65, with mild symptoms; daughter, age 29, asymptomatic. After genetic counseling, ABCA4 and RP1 gene analysis was performed. The results highlighted an important genetic picture. The proband was found to carry two variant RP1 SNPs, rs2293869 (c.2953A>T) and rs61739567 (c.6098G>A), and, a wild-type condition for four RP1 polymorphisms, rs444772 (c.2623G>A) and three SNPs in the ‘hot-spot’ region, exon 4. The proband's wife, instead, showed an opposite condition compared to her husband: a homozygous mutated condition for the first four SNPs analyzed, while the last two were wild-type. Regarding the ABCA4 gene, the proband evidenced a wild-type condition. Furthermore, the wife showed a heterozygous condition of ABCA4 rs3112831 (c.1268A>G). As expected, the daughter presented heterozygosity for all variants of both genes. In conclusion, even though the c.1268A>G missense variant of the ABCA4 gene has often been reported as causative of disease, and in other cases protective of disease, in our family case, the variant appears to reduce or delay the risk of onset of Stargardt disease.