Association of Risk Variants in the CFH Gene With Elevated Levels of Coagulation and Complement Factors in Idiopathic Multifocal Choroiditis

Abstract

Importance: Idiopathic multifocal choroiditis (MFC) is poorly understood, thereby hindering optimal treatment and monitoring of patients.

Objective: To identify the genes and pathways associated with idiopathic MFC.

Design, setting, and participants: This was a case-control genome-wide association study (GWAS) and protein study of blood plasma samples conducted from March 2006 to February 2022. This was a multicenter study involving 6 Dutch universities. Participants were grouped into 2 cohorts: cohort 1 consisted of Dutch patients with idiopathic MFC and controls, and cohort 2 consisted of patients with MFC and controls. Plasma samples from patients with idiopathic MFC who had not received treatment were subjected to targeted proteomics. Idiopathic MFC was diagnosed according to the Standardization of Uveitis Nomenclature (SUN) Working Group guidelines for punctate inner choroidopathy and multifocal choroiditis with panuveitis. Data were analyzed from July 2021 to October 2022.

Main outcomes and measures: Genetic variants associated with idiopathic MFC and risk variants associated with plasma protein concentrations in patients.

Results: This study included a total of 4437 participants in cohort 1 (170 [3.8%] Dutch patients with idiopathic MFC and 4267 [96.2%] controls; mean [SD] age, 55 [18] years; 2443 female [55%]) and 1344 participants in cohort 2 (52 [3.9%] patients with MFC and 1292 [96.1%] controls; 737 male [55%]). The primary GWAS association mapped to the CFH gene with genome-wide significance (lead variant the A allele of rs7535263; odds ratio [OR], 0.52; 95% CI, 0.41-0.64; P = 9.3 × 10-9). There was no genome-wide significant association with classical human leukocyte antigen (HLA) alleles (lead classical allele, HLA-A*31:01; P = .002). The association with rs7535263 showed consistent direction of effect in an independent cohort of 52 cases and 1292 control samples (combined meta-analysis OR, 0.58; 95% CI, 0.38-0.77; P = 3.0 × 10-8). In proteomic analysis of 87 patients, the risk allele G of rs7535263 in the CFH gene was strongly associated with increased plasma concentrations of factor H-related (FHR) proteins (eg, FHR-2, likelihood ratio test, adjusted P = 1.1 × 10-3) and proteins involved in platelet activation and the complement cascade.

Conclusions and relevance: Results suggest that CFH gene variants increase systemic concentrations of key factors of the complement and coagulation cascades, thereby conferring susceptibility to idiopathic MFC. These findings suggest that the complement and coagulation pathways may be key targets for the treatment of idiopathic MFC.

Figure 1.. Subtypes of Idiopathic Multifocal Choroiditis

Fundus photograph in a patient with multifocal choroiditis (A), and a patient with punctate inner choroidopathy (B).

Figure 2.. Overview of All Recruited Patients in Cohorts 1 and 2

For cohort 1, after quality control and case selection, 170 idiopathic cases of multifocal choroiditis were analyzed. ^aInsufficient data for accurate subtype classification between multifocal choroiditis or punctate inner choroidopathy.

Figure 3.. Manhattan and Regional Plot of Genome-Wide Association Analysis of Idiopathic Multifocal Choroiditis or Punctate Inner Choroidopathy

A, Manhattan plot of the results of a genome-wide association study in 170 patients with idiopathic multifocal choroiditis or punctate inner choroidopathy and 4266 Dutch control participants. Each dot represents the result of the association test for a single-nucleotide variation (SNV). On the x-axis, the chromosomes are displayed, and the y-axis represents the −log₁₀ of the P value from a scalable and accurate implementation of generalized mixed model including the covariates age, sex, and the first 6 principal components from ancestry analysis. The blue line indicates the threshold for suggestive association (P < 1.0 × 10⁻⁶), the orange line indicates the threshold for genome-wide significance (P < 5 × 10⁻⁸). One genome-wide significant signal was observed in the CFH gene (20 SNVs; lead variant the A allele of rs7535263). Regional association plot generated in LocusZoom of the CFH region before (B) and after (C) conditioning on rs7535263. On the x-axis, the position on the chromosome is displayed including the position of the genes in this region. The left y-axis represents the −log₁₀(P value) of the results of the association tests, and the right y-axis represents the recombination rate. The lead SNV is plotted as a red dot; other data points are colored according to their r² with the lead SNV.

Figure 4.. Forest Plot Depicting the Summary Statistics of the Association Analysis for Different Disease Groups for the A Allele of rs7535263 in the CFH Gene

Controls for cohort 1 include the 4266 population control participants used in genome-wide association analysis, and controls for cohort 2 include 1292 population control participants. AF indicates allele frequency; MFC, multifocal choroiditis; OR, odds ratio; PIC, punctate inner choroidopathy. ^aInsufficient data for accurate subtype classification between MFC or PIC for 11 cases. ^bResults of a meta-analysis of cohort 1 (n = 170) and cohort 2 (n = 52).

Figure 5.. Association Between the rs7535263 in CFH and Plasma Concentrations of Immune Mediators in Multifocal Choroiditis

EDTA plasma was subjected to targeted 370-plex proteomics array (Olink) in 87 treatment-naive patients with idiopathic multifocal choroiditis or punctate inner choroidopathy. This figure shows the plasma levels for complement factor H (FH) (A), complement factor H–related protein 2 (FHR-2) (B), prothrombin (F2) (C), and apolipoprotein F (APOF) (D) across the genotype of rs7535263 in patients. Protein concentrations are expressed as normalized protein expression (NPX).