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Genetic mechanisms underlying severe retinal dystrophy in a large Swedish family presenting two distinct phenotypes, Leber congenital amaurosis and Stargardt disease were investigated. In the family, four patients with Leber congenital amaurosis were homozygous for a novel c.2557C>T (p.Q853X) mutation in the CRB1 gene, while of two cases with Stargardt disease, one was homozygous for c.5461-10T>C in the ABCA4 gene and another was a compound heterozygous for c.5461-10T>C and a novel ABCA4 mutation c.4773+3 A>G. Sequence analysis of the entire ABCA4 gene in patients with Stargardt disease revealed complex alleles with additional sequence variants.Our results provide evidence of genetic complexity causative of different clinical features present in the same family, which is an obvious challenge for ophthalmologists, molecular geneticists and genetic counsellors.

Retinal degenerations represent a heterogeneous group of disorders affecting the function of the retina. The frequency of retinitis pigmentosa (RP) is 1/3500 worldwide, however, in northern Sweden it is 1/2000 due to limited migration and a 'founder' effect. In this study we identified genetic mechanisms underlying autosomal dominant and recessive RP present in northern Sweden. Several novel mutations unique for this region were found. In an autosomal recessive form of RP, Bothnia dystrophy caused by mutations in the RLBP1 gene, bi-allelic mutations R234W, M226K and compound heterozygosity, M226K+R234W was detected.In dominant form of RP mapped to 19q13.42 a 59 kb genomic deletion including the PRPF31 and three other genes was found.These data provide additional information on the molecular mechanisms of RP evolvement and in the future might be useful in development of therapeutic strategies. Identification of the disease-causing mutations allowed introducing molecular genetic testing of the patients and their families into the clinical practice.