Persistent Tenosynovitis, Steroid Dependency and a Hyperpigmented Scaly Macular Rash in a Child With Juvenile Idiopathic Arthritis.

Blau syndrome is a rare autoinflammatory disease, characterized by granulomatous symmetric arthritis, skin rash and uveitis. It is caused by mutations in the CARD15/NOD2 gene, which is a significant part of innate immunity. We describe the case of a patient with Blau syndrome, initially misdiagnosed as juvenile idiopathic arthritis. Genetic analysis showed R334Q mutation in the NOD2 gene that is known to be linked to Blau syndrome. Our patient was successfully treated with the IL-1β blocking agent canakinumab, with clinical and laboratory remission without any adverse effects. To our knowledge this is one of the rare cases of Blau syndrome successfully treated with canakinumab. After moving abroad, canakinumab was discontinued and she was treated with adalimumab instead. Change in her treatment resulted in a relapse of her disease. Prompt recognition of Blau syndrome and the optimal treatment, are vital for the prevention of severe sequelae such as vision loss and joint deformities. Canakinumab constitutes a promising therapeutic approach for Blau syndrome and requires further investigation.