RESUMEN
The purpose of this study was to analyze and molecularly describe the largest group of patients with ABCA4-associated retinal degeneration in Latin America. Pathogenic variants in ABCA4, a member of the ATP Binding Cassette (ABC) transporters superfamily, is one of the most common causes of inherited visual deficiency in humans. Retinal phenotypes associated with genetic defects in ABCA4 are collectively known as ABCA4-associated retinal degenerations (ABCA4R), a group of recessively inherited disorders associated with a high allelic heterogeneity. While large groups of Caucasian and Asiatic individuals suffering from ABCA4R have been well characterized, molecular information from certain ethnic groups is limited or unavailable, precluding a more realistic knowledge of ABCA4-related mutational profile worldwide. In this study, we describe the molecular findings of a large group of 211 ABCA4R index cases from Mexico. Genotyping was performed using either next generation sequencing (NGS) of a retinal dystrophy genes panel or exome. ABCA4 targeted mutation testing was applied to a subgroup of subjects in whom founder mutations were suspected. A total of 128 different ABCA4 pathogenic variants were identified, including 22 previously unpublished variants. The most common type of genetic variation was single nucleotide substitutions which occurred in 92.7% (408/440 alleles). According to the predicted protein effect, the most frequent variant type was missense, occurring in 83.5% of disease-causing alleles (368/440). Mutations such as p.Ala1773Val are fully demonstrated as a founder effect in native inhabitants of certain regions of Mexico. This study also gives us certain indications of other founder effects that need to be further studied in the near future. This is the largest molecularly characterized ABCA4R Latin American cohort, and our results supports the value of conducting genetic screening in underrepresented populations for a better knowledge of the mutational profile leading to monogenic diseases.
Asunto(s)
Transportadoras de Casetes de Unión a ATP , Genotipo , Degeneración Retiniana , Humanos , Transportadoras de Casetes de Unión a ATP/genética , México , Masculino , Femenino , Degeneración Retiniana/genética , Niño , Mutación , Adulto , Adolescente , Persona de Mediana Edad , Secuenciación de Nucleótidos de Alto Rendimiento , Alelos , Fenotipo , Preescolar , Adulto Joven , LinajeRESUMEN
BACKGROUND: Inherited retinal dystrophies are hereditary diseases which have in common the progressive degeneration of photoreceptors. They are a group of diseases with clinical, genetic, and allelic heterogeneity. There is limited information regarding the genetic landscape of inherited retinal diseases in Mexico, therefore, the present study was conducted in the northeast region of the country. METHODS: Patients with inherited retinal dystrophies were included. A complete history, full ophthalmological and medical genetics evaluations, and genetic analysis through a targeted NGS panel for inherited retinal dystrophies comprising at least 293 genes were undertaken. RESULTS: A total of 126 patients were included. Cases were solved in 74.6% of the study's population. Retinitis pigmentosa accounted for the most found inherited retinal disease. Ninety-nine causal variants were found, being USH2A and ABCA4 the most affected genes (26 and 15 cases, respectively). CONCLUSIONS: The present study documents the most prevalent causative genes in IRDs, as USH2A, in northeastern Mexico. This contrasts with previous reports of IRDs in other zones of the country. Further studies, targeting previously unstudied populations in Mexico are important to document the genetic background of inherited retinal dystrophies in the country.
Asunto(s)
Distrofias Retinianas , Retinitis Pigmentosa , Síndromes de Usher , Humanos , Mutación , México/epidemiología , Distrofias Retinianas/epidemiología , Distrofias Retinianas/genética , Retinitis Pigmentosa/genética , Linaje , Transportadoras de Casetes de Unión a ATP/genéticaRESUMEN
BACKGROUND: Inherited retinal disorders (IRDs) are a complex group of heritable diseases which are characterized by rod, cone, retinal pigment epithelium, or optic nerve dysfunction. Recently, mutations in CLN3 have also been associated with isolated IRDs. Herein, a case with heterozygous CLN3 variations that had not been previously linked to a CLN3-isolated retinal degeneration (CLN3IRD) phenotype in a Hispanic female and its multimodal imaging findings across a 10-year follow-up are presented. MATERIAL AND METHODS: An observational, prospective, case report on a hispanic female with CLN3IRD is presented. Patients underwent genetic testing and color fundus photography (CFC) and autofluorescence (FAF), fluorescein angiography (FA), Spectral domain optical coherence tomography (OCT) of the macular area, electroretinogram (ERG) and 30-2 visual field examination through automated perimetry. RESULTS: A female, aged 24, affected by CLN3IRD phenotype from c.944dup and c.1305C>G compound heterozygous variants, presented with bilateral hypopigmentary changes in the macular area of OU with that corresponded to hyporautofluorescent deposits in the macular area on FAF. An atrophic maculopathy was evident on structural OCT, and FA disclosed a symmetrical macular hyperflourescence with staining in the early and late stages in OU. Humphrey visual field testing showed a marked reduction of the central visual field in OU. Electrophysiological testing revealed an ERG with markedly decreased a and b waves in OU. In ten years follow up developed of bone spiculae in the midperipheral retina. CONCLUSIONS: We reported a patient with a novel CLN3IRD severe phenotype associated with the variants c.944dup and c.1305C>G, which had previously only been associated with JCNL.
Asunto(s)
Degeneración Retiniana , Humanos , Femenino , Degeneración Retiniana/diagnóstico , Degeneración Retiniana/genética , Estudios Prospectivos , Glicoproteínas de Membrana/genética , Mutación , Electrorretinografía , Heterocigoto , Fenotipo , Hispánicos o Latinos/genética , Tomografía de Coherencia Óptica , Angiografía con Fluoresceína , Chaperonas Moleculares/genéticaRESUMEN
BACKGROUND: Retinoblastoma (Rb) most frequently presents as a unilateral sporadic disease up to 40% of cases, however, arise from a monoallelic germline pathogenic variant. Only 10% of the germline mutations are inherited, and high penetrance is seen in up to 90% of these cases. As an effort to optimize counseling and screening, mutations are classified according to inheritance patterns. However, RB1 spectrum is highly heterogeneous, and information for unaffected carriers remains scarce. MATERIALS AND METHODS: The Mexican family of a 5-month-old patient diagnosed with Rb was studied. The family consisted of five individuals (father, mother, and three siblings). Genetic testing using a next-generation sequencing assay targeting RB1 with oligonucleotide baits designed to capture its exons and 20 bases flanking intronic sequences was performed in every family member. Clinical history and a complete ophthalmological examination (best-corrected visual acuity, slit-lamp biomicroscopy, macular optical coherence tomography, fundus autofluorescence, optical coherence tomography angiography, and electrophysiological studies) were performed in members testing positive to RB1 mutation. RESULTS: The father and her five-month-old daughter tested positive for a non-synonymous RB1 mutation c.459del (p.Lys154Serfs*21). The girl presented with bilateral retinoblastoma, successfully treated with cryotherapy and intravenous chemotherapy. The father had no relevant findings on imaging studies or ophthalmologic evaluation. CONCLUSIONS: This report describes a rare case of a novel low-penetrance RB1 germline mutation. Long-term follow-up of the father will include periodic evaluation of the eyes and orbits, and surveillance for systemic sarcoma and secondary malignancies. Implications for unaffected individuals need to be further studied.