Equipe MitoLab, Unité MitoVasc, INSERM U1083, CHU d'Angers, CNRS 6015, Université d'Angers, 49933, Angers, France.
Genomics and Human Genetics Laboratory, Institut Pasteur du Maroc, Casablanca, Morocco.
Orphanet J Rare Dis. 2022 May 12;17(1):197. doi: 10.1186/s13023-022-02340-7.
BACKGROUND: Inherited retinal dystrophies (IRD) and optic neuropathies (ION) are the two major causes world-wide of early visual impairment, frequently leading to legal blindness. These two groups of pathologies are highly heterogeneous and require combined clinical and molecular diagnoses to be securely identified. Exact epidemiological studies are lacking in North Africa, and genetic studies of IRD and ION individuals are often limited to case reports or to some families that migrated to the rest of the world. In order to improve the knowledge of their clinical and genetic spectrums in North Africa, we reviewed published data, to illustrate the most prevalent pathologies, genes and mutations encountered in this geographical region, extending from Morocco to Egypt, comprising 200 million inhabitants. MAIN BODY: We compiled data from 413 families with IRD or ION together with their available molecular diagnosis. The proportion of IRD represents 82.8% of index cases, while ION accounted for 17.8%. Non-syndromic IRD were more frequent than syndromic ones, with photoreceptor alterations being the main cause of non-syndromic IRD, represented by retinitis pigmentosa, Leber congenital amaurosis, and cone-rod dystrophies, while ciliopathies constitute the major part of syndromic-IRD, in which the Usher and Bardet Biedl syndromes occupy 41.2% and 31.1%, respectively. We identified 71 ION families, 84.5% with a syndromic presentation, while surprisingly, non-syndromic ION are scarcely reported, with only 11 families with autosomal recessive optic atrophies related to OPA7 and OPA10 variants, or with the mitochondrial related Leber ION. Overall, consanguinity is a major cause of these diseases within North African countries, as 76.1% of IRD and 78.8% of ION investigated families were consanguineous, explaining the high rate of autosomal recessive inheritance pattern compared to the dominant one. In addition, we identified many founder mutations in small endogamous communities. SHORT CONCLUSION: As both IRD and ION diseases constitute a real public health burden, their under-diagnosis in North Africa due to the absence of physicians trained to the identification of inherited ophthalmologic presentations, together with the scarcity of tools for the molecular diagnosis represent major political, economic and health challenges for the future, to first establish accurate clinical diagnoses and then treat patients with the emergent therapies.
背景:遗传性视网膜病变(IRD)和视神经病变(ION)是全球范围内导致早期视力损害的两个主要原因,经常导致法定失明。这两组病变高度异质,需要结合临床和分子诊断才能明确诊断。北非缺乏确切的流行病学研究,IRD 和 ION 个体的遗传研究通常仅限于病例报告或一些迁移到世界其他地区的家庭。为了提高我们对北非临床和遗传谱的认识,我们回顾了已发表的数据,以说明在这个地理区域(从摩洛哥到埃及,有 2 亿居民)中最常见的疾病、基因和突变。
主要内容:我们汇集了 413 个有 IRD 或 ION 家族的资料,并对其进行了可用的分子诊断。IRD 病例占 82.8%,而 ION 占 17.8%。非综合征性 IRD 比综合征性 IRD 更为常见,光感受器改变是主要的非综合征性 IRD 原因,包括色素性视网膜炎、先天性黑矇和 Cone-Rod 营养不良,而纤毛病变是综合征性 IRD 的主要部分,其中 Usher 和 Bardet-Biedl 综合征分别占 41.2%和 31.1%。我们确定了 71 个 ION 家族,84.5%有综合征表现,而令人惊讶的是,非综合征性 ION 报道甚少,仅有 11 个家族与常染色体隐性视神经萎缩有关,与 OPA7 和 OPA10 变异或与线粒体相关的 Leber ION 有关。总的来说,近亲结婚是北非国家这些疾病的主要原因,因为在调查的 IRD 和 ION 家族中,有 76.1%和 78.8%是近亲结婚的,这解释了与显性遗传模式相比,常染色体隐性遗传模式的高发生率。此外,我们在小的、近亲结婚的社区中发现了许多创始突变。
简短结论:由于 IRD 和 ION 疾病都构成了真正的公共卫生负担,由于缺乏专门识别遗传性眼科表现的医生,北非的诊断不足,以及分子诊断工具的缺乏,这是未来的重大政治、经济和健康挑战,首先要建立准确的临床诊断,然后用新兴疗法治疗患者。
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