Congenital stationary night blindness, a nonprogressive retinal disorder characterized by impaired night vision and ocular symptoms such as myopia, hyperopia, nystagmus, and reduced visual acuity, can be classified into 2 types: a complete form (see CSNB1, 310500) and ... Congenital stationary night blindness, a nonprogressive retinal disorder characterized by impaired night vision and ocular symptoms such as myopia, hyperopia, nystagmus, and reduced visual acuity, can be classified into 2 types: a complete form (see CSNB1, 310500) and an incomplete form (see CSNB2, 300071) (Zeitz et al., 2006). These 2 subtypes can be diagnosed by electroretinography (ERG) and by molecular means. CSNB type 2 is associated with reduced rod b-wave, a substantially reduced cone a-wave, and a reduced 30-Hz flicker ERG response, whereas the oscillatory potentials are normal. CSNB type 2 is associated with mutations in the CACNA1F gene (300110). A large degree of genetic heterogeneity in CSNB is indicated by the observation that routine screening for all known genes associated with CSNB leaves a certain percentage of cases unresolved. Zeitz et al. (2006) described 3 patients with CSNB type 2 from 2 unrelated families. The first family consisted of the index patient and his affected brother, 4 unaffected sibs, and their unaffected parents. The 2 patients presented with nystagmus and decreased visual acuity in early childhood. In both patients at age 15 years, best corrected visual acuity was 20/100 in both eyes. The disease course in the index patient was stationary for 30 years, however, he experienced a decrease in visual acuity near the time of the report. Neither patient complained about night blindness, and only the index patient developed moderate photophobia accompanied by a mild decrease in visual acuity. The 2 brothers were 39 and 45 years old at the time of the report. The index patient of the second family was the only affected member. He reported decreased visual acuity and night blindness at age 15 years. Visual acuity was reduced to 20/30 in both eyes. Electroretinography (ERG) showed a pattern typical for CSNB in general, with a well developed a-wave but a minimal b-wave.
Zeitz et al. (2006) detected mutations in the CABP4 gene in both families examined with CSNB2B. The affected brothers in the first family were homozygous for a 2-bp deletion (800-801delAG; 608965.0001); the patient from the first family carried ... Zeitz et al. (2006) detected mutations in the CABP4 gene in both families examined with CSNB2B. The affected brothers in the first family were homozygous for a 2-bp deletion (800-801delAG; 608965.0001); the patient from the first family carried the 2-bp deletion and a C-to-T transition in exon 2 (370C-T; 608965.0002) in compound heterozygosity. Zeitz et al. (2006) showed that these mutations reduced CABP4 transcript levels to 30 to 40% of those in controls. On the basis of haplotype reconstruction and the Swiss ancestry of both families, a common origin of the 2-bp deletion in all 3 apparently unrelated individuals was considered possible.