Genetic and Clinical Features of Blau Syndrome among Chinese Patients with Uveitis

Abstract

Purpose: The American College of Medical Genetics and Genomics (ACMG) and the Association for Molecular Pathology call for cautious interpretation of variants as causative of a monogenic disorder by stringent standards. We aimed to reclassify the pathogenicity of nucleotide binding oligomerization domain containing 2 (NOD2) variants according to the ACMG guidelines and to characterize clinical features in patients whose ocular disease might actually be explained by Blau syndrome.

Design: Genetic analysis and descriptive study.

Participants: A total of 1003 unrelated healthy individuals and 3921 sporadic patients who presented with uveitis.

Methods: Whole-exome sequencing was performed on all healthy participants and 551 patients with uveitis, and targeted NOD2 resequencing was performed on the remaining 3370 patients with uveitis. Pathogenicity for Blau syndrome was classified for NOD2 variants identified by sequencing in study participants according to the ACMG guidelines. Clinical manifestations were compared among NOD2 variants of different levels of classification.

Main outcome measures: Pathogenicity of variants.

Results: Eight NOD2 gain-of-function mutations, p.R334W, p.R334Q, p.E383K, p.G481D, p.W490S, p.M513T, p.R587C, and p.N670K, were classified as pathogenic, and 66 patients (1.7%) with uveitis were diagnosed with Blau syndrome due to these mutations. Of 66 with Blau syndrome, anterior uveitis accounted for 39.4%, posterior uveitis for 9.1%, and panuveitis for 51.5%. A proportion of 21.2% of Blau syndrome presented as multifocal choroiditis, 48.5% had papillitis, and 74.2% showed retinal microvasculitis detected by fundus fluorescein angiography. Six NOD2 variants, p.P268S, p.R311W, p.R471C, p.A612T, p.R702W, and p.V955I, were considered nonpathogenic for Blau syndrome and were identified in 96 patients with uveitis. The incidence of bilateral uveitis (86.4%), secondary glaucoma (47.0%), epiretinal membrane (7.6%), choroidal neovascularization (4.6%), retinal atrophy (10.6%), arthritis (69.7%), joint deformity (51.5%), and skin rash (40.9%) was higher in Blau syndrome than in patients with uveitis carrying non-Blau-causing NOD2 variants. Patients with Blau syndrome permanently experienced overall poorer best-corrected visual acuity. Several rare NOD2 mutations, p.I722L (2 cases), p.T476P (1 case), p.T476del (1 case), and p.R439H (1 case), were newly identified.

Conclusions: Pathogenic NOD2 variants for Blau syndrome were limited to those gain-of-function mutations and were associated with a high risk for arthritis, skin rash, permanent visual loss, and ocular complications in patients with uveitis.

Keywords: Blau syndrome; Genetic Variant; NOD2; Uveitis.