Abstract
Blau syndrome (BS) is a rare monogenic granulomatous autoinflammatory disease (a variant of genetically determined sarcoidosis) caused by a mutation of the NOD2/CARD15 gene, transmitted in an autosomal dominant manner and manifested by a triad of signs: dermatitis, granulomatous arthritis with pronounced exudative component and involvement of periarticular tissues, uveitis. Objective of the study: to present the variants of the clinical picture and the type of pathogenic variants (mutations) in patients with a rare monogenic granulomatous autoinflammatory disease – BS – in the Russian Federation, the clinical picture of which can mimic juvenile idiopathic arthritis. Materials and methods of research: the observational study included patients with BS who were observed in the children's department of the V.A. Nasonova Research Institute of Rheumatology from 2014 to 2021, the diagnosis of which was confirmed by the detection of a pathogenic mutation in the NOD2/CARD15 gene. Results: the study included 8 children: 6 boys and 2 girls. Ethnic Russians were 5 patients, 1 Jew, 1 of mixed origin (peoples of Dagestan/Russians), 1 Tatar female. The age of onset of the disease is from the first days of life to 2,5 years. Skin lesions were observed in 6 (75%) patients. Atypical arthritis (boggy arthritis) was observed in all patients, in all cases the wrist, ankle and knee joints were involved in the pathological process. Uveitis developed after all other manifestations and was detected in 6 (75%) patients. At the onset, 5 patients had anterior uveitis, 2 of them with subsequent involvement of the posterior segment; in 1 child, the first ophthalmic manifestation was posterior uveitis. In 5 patients, there was no increase in acute phase markers (ESR, C-reactive protein). 5 (62,5%) patients had variant p.R334Q (c.1001G>A), 2 (25%) had variant p.R334W (c.1001G>A), 1 patient had variant p.M513T (c.1538T>C) of the NOD2/CARD15 gene. Conclusions: BS can be encountered in the practice of a pediatric rheumatologist in Russia and requires differentiation from polyarticular juvenile idiopathic arthritis. Identification of the pathogenic variant of the NOD2/CARD15 gene plays a decisive role in the diagnosis.
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