Ocular Characteristics and Genotype-Oriented Disease Spectrum of Alström Syndrome in Taiwan

This study aimed to describe the ophthalmological features of Alström syndrome, a rare syndromic ciliopathy, and to delineate the genotype-associated disease spectrum.

Eight Taiwanese patients were recruited for this study. Pathogenic variants were identified using next-generation sequencing, and medical records were reviewed for systemic involvement. Best-corrected visual acuity, cycloplegic refraction, blue light fundus autofluorescence imaging, International Society for Clinical Electrophysiology of Vision-standard full-field flash electroretinography, optical coherence tomography, and visual field testing were obtained and studied retrospectively.

Common ocular manifestations included hyperopia, nystagmus, photophobia, and visual impairment. Most patients also exhibited obesity, sensorineural hearing loss, and developmental delays. Phenotype variability was observed in age of onset (0-8 years), severity of visual impairment, and extent of extraocular involvement. Electroretinography results reflected varying degrees of retinal degeneration. We identified c.11110_11128del as a genotype frequently occurring in Asian populations that demonstrated a more severe phenotype within our cohort. In addition, we discovered three novel variants, including a LINE-1 insertion in exon 8 (c.3565insL1), c.6166_6167insAT, and 8077del.

Alström syndrome may manifest with early-onset ocular and syndromic features, or demonstrate a later onset with limited extraocular involvement. This is the first report of a LINE-1 insertion in ALMS1, with affected patients exhibiting comparatively mild phenotypes.

Combined ophthalmological and extraocular phenotypes combined may aid in diagnosing this rare disease and differentiating it from other possible causes.