Incidence and natural history of proliferative sickle cell retinopathy:Observations from a cohort study

Objective: To describe the incidence, prevalence, and natural history of proliferative sickle cell retinopathy (PSR). Design: Prospective longitudinal study over 20 years. Participants: Newborn screening of 100000 consecutive deliveries from 1973 to 1981 identified 315 children with homozygous sickle cell (SS) disease and 201 with SS-hemoglobin C (SC) disease. By the age of 5 years, 307 SS patients and 166 SC patients were alive and living in Jamaica and were recruited for this ophthalmic study. Methods: Description of retinal vascular changes on annual angiography and angioscopy. Main Outcome Measures: Incidence and prevalence of PSR and its behavior on follow-up. Progression of PSR was investigated using the number of eyes affected (none, one, both) and the interval until PSR onset. Results: At last review in January 2000, PSR had developed in 59 patients (14 SS, 45 SC), unilaterally in 36 patients and bilaterally in 23. Incidence increased with age in both genotypes, with crude annual incidence rates of 0.5 cases (95% confidence interval [CI], 0.3-0.8) per 100 SS subjects and 2.5 cases (95% CI, 1.9-3.3) per 100 SC subjects. Prevalence was greater in SC disease, and by the ages of 24 to 26 years, PSR had occurred in 43% subjects with SC disease and in 14% subjects with SS disease. Patients with unilateral PSR had a 16% (11% SS, 17% SC) probability of regressing to no PSR and a 14% (16% SS, 13% SC) probability of progressing to bilateral PSR. Those with bilateral PSR had an 8% (8% SS, 8% SC) probability of regressing to unilateral PSR and a 1% (0 SS, 2% SC) probability of regressing to a PSR-free state. Irretrievable visual loss occurred in only 1 of 82 PSR-affected eyes, and 1 required detachment surgery and recovered normal visual acuity. Conclusions: Longitudinal observations over 20 years in a cohort of patients followed from birth confirms a greater incidence and severity of PSR in SC disease, and shows that spontaneous regression occurred in 32% of PSR-affected eyes. Permanent visual loss was uncommon in subjects observed up to the age of 26 years. © 2005 by the American Academy of Ophthalmology.

Partitioning Heritability of Regulatory and Cell-Type-Specific Variants across 11 Common Diseases

Regulatory and coding variants are known to be enriched with associations identified by genome-wide association studies (GWASs) of complex disease, but their contributions to trait heritability are currently unknown. We applied variance-component methods to imputed genotype data for 11 common diseases to partition the heritability explained by genotyped SNPs () across functional categories (while accounting for shared variance due to linkage disequilibrium). Extensive simulations showed that in contrast to current estimates from GWAS summary statistics, the variance-component approach partitions heritability accurately under a wide range of complex-disease architectures. Across the 11 diseases DNaseI hypersensitivity sites (DHSs) from 217 cell types spanned 16% of imputed SNPs (and 24% of genotyped SNPs) but explained an average of 79% (SE = 8%) of  from imputed SNPs (5.1× enrichment; p = 3.7 × 10⁻¹⁷) and 38% (SE = 4%) of  from genotyped SNPs (1.6× enrichment, p = 1.0 × 10⁻⁴). Further enrichment was observed at enhancer DHSs and cell-type-specific DHSs. In contrast, coding variants, which span 1% of the genome, explained <10% of  despite having the highest enrichment. We replicated these findings but found no significant contribution from rare coding variants in independent schizophrenia cohorts genotyped on GWAS and exome chips. Our results highlight the value of analyzing components of heritability to unravel the functional architecture of common disease.