الملخص الإنجليزي
In Oman, the causes of visual impairment are changing from communicable treatable diseases to incurable chronic ones with lifelong consequences. Although improved health services and initiatives have assisted in lowering some of the visual impairment cases, further intervention is needed as the transition to NCD continues.
Environmental factors (e.g. ultraviolet radiation) play a role in ocular disease manifestation, but there are genetic components associated with NCD. This becomes an issue of personal, societal, and governmental concern when disease-causing alleles are at high frequencies in the populations. Cultural preferences, such as consanguineous marriages (56.4% of all unions in Oman), endogamous unions, and bearing of many children, might increase allele frequencies in a population. As these practices are common in Middle Eastern countries the chances of individuals inheriting a recessive disease trait and possibly several ancestral disease alleles is elevated. Homozygosity or autozygosity mapping is a suitable method for disease gene detection in most cases. It can be used for the identification of known or novel variations in autosomal recessive conditions, even if a singleton sample pool is available. An example of this is the detection of a new variant in the FAM161A gene of a Palestinian family causing retinitis pigmentosa.5 Homozygosity mapping in combination with exome sequencing is also an option. Although exome sequencing has limitations, such as the difficulty in distinguishing disease from non-disease causing variants, it compensates for limitations associated with homozygosity mapping, where dominant, X-linked and compound heterozygous mutations cannot be detected. Both approaches have been used to identifiy a novel autosomal recessive retinitis pigmentosa variant with late-onset hearing loss in a Middle Eastern family.
