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Purpose: To determine the genetic and genomic alterations underlying classic aniridia in Saudi Arabia, a region with social preference for consanguineous marriage., Methods: Prospective study of consecutive patients referred to a pediatric ophthalmologist in Saudi Arabia (2005-2009). All patients had paired box gene 6 (PAX6) analysis (sequencing and multiplex ligation-dependent probe amplification analysis if sequencing was normal). If PAX6 analysis was negative, the following were performed: candidate gene sequencing (forkhead box C1 [FOXC1], paired-like homeodomain transcription factor 2 [PITX2], cytochrome P450, family 1, subfamily B [CYP1B1], paired-like homeodomain transcription factor 3 [PITX3], and v-maf avian musculoaponeurotic fibrosarcoma oncogene homolog [MAF]) and molecular karyotyping by array competitive genomic hybridization (250K single nucleotide polymorphism (SNP) arrays)., Results: All 12 probands (4 months-25 years of age; four boys and eight girls) had lens opacity and foveal hypoplasia in addition to no grossly visible iris. Four cases were familial. All cases were products of consanguineous unions except for three, one of which was endogamous. Heterozygous PAX6 mutations (including two novel mutations) were detectable in all but two cases, both of which were sporadic. In one of these two cases, the phenotype segregated with homozygosity for a previously-reported pathogenic missense FOXC1 variant (p.P297S) when homozygosity for chromosome 11q24.2 deletion (chr11:125,001,547-125,215,177 [rs114259885; rs112291840]) was also present. In the other, no genetic or genomic abnormalities were found., Conclusions: The classic aniridia phenotype in Saudi Arabia is typically caused by heterozygous PAX6 mutations, even in the setting of enhanced homozygosity from recent shared parental ancestry. For PAX6-negative cases, interaction between missense variation in an anterior segment developmental gene and copy number variation elsewhere in the genome may be a potential mechanism for the phenotype.

Purpose: To clinically and genetically characterize a distinct phenotype of congenital megalocornea (horizontal corneal diameter ≥13 mm) with secondary glaucoma from spherophakia and/or ectopia lentis during childhood in affected Saudi families., Methods: Clinical exam, homozygosity scan, and candidate gene analysis., Results: From 2005 to 2010, eight affected individuals from three consanguineous families were identified. In addition to congenital megalocornea, affected children presented with secondary glaucoma from spherophakia and/or ectopia lentis. One member from each family developed spontaneous complete crystalline lens dislocation into the anterior chamber with associated acute glaucoma during early childhood. Older individuals had phenotypes that would have suggested prior uncontrolled primary congenital/infantile glaucoma had past ophthalmic and/or family histories not been available. Homozygosity mapping performed for the first two families suggested the candidate gene latent transforming growth factor-beta-binding protein 2 (LTBP2), which when sequenced revealed a novel homozgyous mutation that segregated with the phenotype in each family (p.S338PfsX4 [c.1012delT], p.Q1619X[(c.4855C>T]). LTBP2 sequencing in the third family revealed a third novel homozygous mutation (p.C1438Y [c.4313G>A])., Conclusions: Congenital megalocornea with childhood secondary glaucoma from spherophakia and/or ectopia lentis is a distinct condition caused by recessive LTBP2 mutations that needs to be distinguished from buphthalmos secondary to primary congenital/infantile glaucoma because typical initial surgical treatment is lens removal in the former and angle surgery in the latter. Complete dislocation of the crystalline lens into the anterior chamber during early childhood can occur in young children with this unique phenotype.

Purpose: To report the clinical phenotype in patients with a retinal dystrophy associated with novel mutations in the MER tyrosine kinase (MERTK) gene., Methods: A consanguineous family of Middle Eastern origin was identified, and affected members underwent a full clinical evaluation. Linkage analysis was performed using the Affymetrix 50K chip. Regions of homozygosity were identified. The positional candidate genes protocadherin 21 (PCDH21), retinal G protein-coupled receptor (RGR), and MERTK were polymerase chain reaction (PCR) amplified and sequenced. Long-range PCR was performed to characterize the deletion. Two hundred and ninety-two probands with autosomal recessive, childhood onset, retinal dystrophies were analyzed using the Asper Ophthalmics Leber congenital amaurosis chip to screen for known MERTK mutations., Results: Analysis of a 50K-Affymetrix whole genome scan identified three regions of homozygosity on chromosomes 2 and 10. Screening of the candidate gene MERTK showed a possible deletion of exon 8. Long-range PCR identified a ~9 kb deletion within MERTK that removes exon 8. Screening of DNA from a panel of Saudi Arabian patients with autosomal recessive retinitis pigmentosa identified a second consanguineous family with the same mutation. One patient with a known MERTK mutation (p.R651X) was identified using the Asper Ophthalmics Leber congenital amaurosis chip. Further screening of the gene identified a second novel splice site mutation in intron 1. The phenotype associated with these identified MERTK mutations is of a childhood onset rod-cone dystrophy with early macular atrophy. The optical coherence tomography (OCT) appearance is distinctive with evidence of debris beneath the sensory retina., Conclusions: Mutations in MERTK are a rare cause of retinal dystrophy. Non homologous recombination between Alu Y repeats near or within disease genes may be an important cause of retinal dystrophies.

Purpose: To describe the finding of a novel calcium binding protein 4 (CABP4) mutation in a family with Leber congenital amaurosis (LCA) phenotype., Methods: Homozygosity mapping was performed in a consanguineous family with four affected members originally referred as cases of LCA. Detailed electroretinographic recordings were obtained., Results: A novel homozygous single base-pair insertion was identified in all four siblings. The patients had an LCA-like phenotype, including either flat or greatly diminished electroretinographic activity., Conclusions: This report significantly expands on the phenotype associated with calcium binding protein 4 mutations, which has so far been limited to congenital stationary night blindness, and further demonstrates how molecular data often blur the boundaries between what are believed to be clinically distinct retinal disorders.

Purpose: To catalog mutations that underlie retinitis pigmentosa (RP) in Saudi Arabia using a representative sample., Methods: Fifty-two patients with RP were recruited and their homozygosity mapping, with or without linkage analysis, was used to suggest the causative genes followed by bidirectional sequencing., Results: Mutations were identified in 94% of our study cohort, including seven that were novel., Conclusions: Homozygosity mapping is an extremely robust approach in the study of retinitis pigmentosa in the setting of high rates of consanguinity. BBS3 mutations can rarely present as nonsyndromic RP.

Purpose: To assess for gammaD-crystallin (CRYGD) mutation in 2 Saudi patients with cerulean cataract and in a brother of one of the patients who had coralliform cataract., Methods: Patients and all of their available relatives underwent ophthalmic examination and subsequent sequencing of the candidate gene CRYGD., Results: In the first family, a 4-year-old boy with bilateral cerulean cataract and his 6-year-old brother with similar bluish lens discoloration but in a coralliform pattern were heterozygous for the p.P23T CRYGD mutation. Their father and 2 older brothers, all of whom underwent childhood cataract surgery, also harbored the mutation while the 2 asymptomatic immediate family members did not. In the second family, a 7-year-old girl with bilateral cerulean cataract was heterozygous for the same CRYGD mutation. Details of her family history were limited. The patients in the two families shared a common disease haplotype., Conclusions: This first report of p.P23T CRYGD mutation underlying cerulean cataract in the Saudi population strongly supports the mutation's relation with the phenotype. Coralliform cataract can represent variable expressivity for the same mutation rather than a distinct entity.