Human retinal disease from AIPL1 gene mutations: foveal cone loss with minimal macular photoreceptors and rod function remaining.

Objective: To determine the human retinal phenotype caused by mutations in the gene encoding AIPL1 (Aryl hydrocarbon receptor-interacting protein-like 1) now that there are proof-of-concept results for gene therapy success in Aipl1-deficient mice.

Methods: Leber congenital amaurosis (LCA) patients (n = 10) and one patient with a later-onset retinal degeneration (RD) and AIPL1 mutations were studied by ocular examination, retinal imaging, perimetry, full-field sensitivity testing, and pupillometry.

Results: The LCA patients had severe visual acuity loss early in life, nondetectable electroretinograms (ERGs), and little or no detectable visual fields. Hallmarks of retinal degeneration were present in a wide region, including the macula and midperiphery; there was some apparent peripheral retinal sparing. Cross-sectional imaging showed foveal cone photoreceptor loss with a ring of minimally preserved paracentral photoreceptor nuclear layer. Features of retinal remodeling were present eccentric to the region of detectable photoreceptors. Full-field sensitivity was reduced by at least 2 log units, and chromatic stimuli, by psychophysics and pupillometry, revealed retained but impaired rod function. The RD patient, examined serially over two decades (ages, 45-67 years), retained an ERG in the fifth decade of life with abnormal rod and cone signals; and there was progressive loss of central and peripheral function.

Conclusions: AIPL1-LCA, unlike some other forms of LCA with equally severe visual disturbance, shows profound loss of foveal as well as extrafoveal photoreceptors. The more unusual late-onset and slower form of AIPL1 disease may be better suited to gene augmentation therapy and is worthy of detection and further study.