Unique phenotypic–genotypic correlation in Saudi patients with ALMS1 mutations

Abstract

Mutations in the ALMS1 gene have been linked to isolated inherited retinal dystrophy or Alström syndrome. This report illustrates the unique pattern of ALMS1‑associated diseases in a set of three simplex Saudi patients originating from unrelated consanguineous families. A detailed ophthalmological assessment was performed at the Department of Ophthalmology at King Saud University, Riyadh, Saudi Arabia. Next‑generation sequencing vision panel revealed recessive ALMS1 mutations (reference sequence NM_015120). As a result, three distinct pathogenic ALMS1 mutations were identified; the first one is a nonsense mutation (c.8158C>T: p.R2720X) which has recently been identified in a Chinese patient, while the other two are known to have a founder effect in the Saudi population (the frameshift: C.848dupA: p.E283fs and the splicing: C.11870‑2A>T: p.?). Clinically, a prominent nerve fiber layer was observed in the three studied patients with variable expectations of vessel attenuation. In addition, two of our patients observed unusual presentation of specific retinal pigment epithelium pigmentations in semi/halo‑arrangement around the macula. Thus far, our report expands the phenotypic–genotypic spectrum of ALMS1‑associated diseases and supports the principles of applying precision medicine in Saudi Arabia by utilizing the fact that common founder mutations were identified and unique phenotype was observed.