No Choroidal Disease Gene Screening Analysis And Clinical Phenotype

Purpose To identify the disease-causing mutations of10Chinese families with choroideremia (CHM), to characterize the clinical features of13Chinese families with CHM, and to study the correlation between genotype and phenotype.Methods A sample of patients diagnosed as CHM in Peking Union Medical College Hospital during2009to2013was collected.1. Clinical study:Medical history and family history were recorded, and patients were given general ophthalmic examination, including vision acuity, optometry, anterior segment and fundus examination. Special ophthalmic examination was also conducted, including color vision disturbance, fundus photograph, optical coherence tomography (OCT), fundus antofluorescence (AF), electroretinogram (ERG) and visual field (VF).2. Genetic study:Venous blood samples (6-8ml) from patients, family members and matched healthy volunteers were collected. Genomic DNA was isolated from peripheral leukocytes. The coding exons and intron-exon boundaries of CHM gene were amplified by polymerase chain reaction (PCR) and sequenced directly. When mutations were found, single nucleotide polymorphism (SNP) analysis was performed in order to exclude polymorphisms. Whether the mutations had been reported was determined by searching for genetics databases and published papers. If the mutation was novel, we amplified the loci and sequenced it in at lease100normal chromosomes without consanguinity relationship, in order to exclude the unknown population polymorphisms.Results1. Thirteen families with CHM were collected, out of which51male patients and52female carriers were identified. Clinical study was performed in24male patients and21female carriers.87.5%of male patients had night blindness in the first or second decades of life, while46.7%of them had color vision disturbance. The best-corrected visual acuity (BCVA) ranged from light perception (LP) to1.0. The atrophy of the choroid and RPE is the main fundus appearance of male patiences. The macula can be nearly normal, or showed macula dystrophy. A large amount of irregular pigmentary changes were found in two patients. The OCT:The signal of IS/OS and RPE disappeared. A flat and enlarged fovea with the reduced retinal thickness was found in severe male patients. AF showed normal signal of fluorescence in macula in most of male patients. ERG:the rod response was non-detectable in83.3%of the affected eyes, while the cone response was non-detectable in58.3%of the affected eyes. None of the female carriers had night blindness and color vision disturbance. The BCVA of them ranged from0.3to1.5. The patchy fundal pigmentation was the main fundus appearance of female carriers. The pigmentation similar to drusen was found is some of them. OCT:most of the female carriers had normal OCT images. Some local high signals in RPE layer correspond to the drusen. AF showed patchy low signal of fluorescence.2. Mutation analyses of the CHM gene revealed10types of mutations including3nonsense mutations,5splicing mutations,1small deletions mutation and1small indels mutation in10families.70%of them were novel mutations.Conclusion1.Clinical feature:male patients usually have night blindness in the first or second decades of life. BCVA will decrease with age. Patients with bad color vision appeared to have worse BCVA. The atrophy of the choroid and RPE is a common fundus appearance. The macula can subsequently atrophy in the late stage. Female carriers are mostly asymptomatic. The patchy fundal pigmentation is very common in female carriers.2. Genotype-phenotype:CHM is clinically and genetically heterogeneous, the same phenotype can contribute to different mutations, and the similar mutations can lead to different clinical manifestations. The relationship between genotype and phenotype still needs further study.