A novel mutation in early‐onset sarcoidosis/Blau syndrome: an association with Propionibacterium acnes

• Main Authors: Fumiko Okazaki, Hiroyuki Wakiguchi, Yuno Korenaga, Tamaki Nakamura, Hiroki Yasudo, Shohei Uchi, Ryoji Yanai, Nobuyuki Asano, Yoshinobu Hoshii, Tsuyoshi Tanabe, Kazushi Izawa, Yoshitaka Honda, Ryuta Nishikomori, Keisuke Uchida, Yoshinobu Eishi, Shouichi Ohga, Shunji Hasegawa
• Format: Article
• Language: English
• Published: BMC 2021-02-01
• Series: Pediatric Rheumatology Online Journal
• Subjects: D512V mutation; Granulomatous disease; Methotrexate; NF-κB; NOD2; Cutibacterium acnes
• Online Access: https://doi.org/10.1186/s12969-021-00505-5

Abstract Background Early-onset sarcoidosis (EOS) and Blau syndrome (BS) are systemic inflammatory granulomatous diseases without visible pulmonary involvement, and are distinguishable from their sporadic and familial forms. The diseases are characterized by a triad of skin rashes, symmetrical polyarthritis, and recurrent uveitis. The most common morbidity is ocular involvement, which is usually refractory to conventional treatment. A gain-of-function mutation in the nucleotide-binding oligomerization domain-containing protein 2 (NOD2) gene has been demonstrated in this disease; however, little is known about the relationship between the activation of NOD2 and the pathophysiology of EOS/BS. Here we describe EOS/BS with a novel mutation in the NOD2 gene, as well as detection of Propionibacterium acnes (P. acnes) in the granulomatous inflammation. Case presentation An 8-year-old Japanese girl presented with refractory bilateral granulomatous panuveitis. Although no joint involvement was evident, she exhibited skin lesions on her legs; a skin biopsy revealed granulomatous dermatitis, and P. acnes was detected within the sarcoid granulomas by immunohistochemistry with P. acnes-specific monoclonal (PAB) antibody. Genetic analyses revealed that the patient had a NOD2 heterozygous D512V mutation that was novel and not present in either of her parents. The mutant NOD2 showed a similar activation pattern to EOS/BS, thus confirming her diagnosis. After starting oral prednisolone treatment, she experienced an anterior vitreous opacity relapse despite gradual prednisolone tapering; oral methotrexate was subsequently administered, and the patient responded positively. Conclusions We presented a case of EOS/BS with a novel D512V mutation in the NOD2 gene. In refractory granulomatous panuveitis cases without any joint involvement, EOS/BS should be considered as a differential diagnosis; genetic analyses would lead to a definite diagnosis. Moreover, this is the first report of P. acnes demonstrated in granulomas of EOS/BS. Since intracellular P. acnes activates nuclear factor-kappa B in a NOD2-dependent manner, we hypothesized that the mechanism of granuloma formation in EOS/BS may be the result of NOD2 activity in the presence of the ligand muramyl dipeptide, which is a component of P. acnes. These results indicate that recognition of P. acnes through mutant NOD2 is the etiology in this patient with EOS/BS.