[Mutations of NOD2 gene and clinical features in Chinese Blau syndrome patients]

Blau syndrome (BS), an autosomal dominant inherited autoinflammatory disease, is caused by NOD2 mutations. This study aimed to analyze NOD2 gene of suspected BS patients to make definite diagnosis, find NOD2 mutation types and clinical features of Chinese BS cases, and find some clinical indications to identify BS by comparing BS and non-BS cases.

Eighteen suspected BS children (7 boys and 11 girls, age of first visit was from 1 y 8 m to 9 y 6 m) who visited Peking Union Medical College Hospital from 2006 to 2014 and their parents's DNA were extracted from 4 ml blood specimens. PCR was performed for exon 4 of NOD2 and PCR products were purified by 2% gel electrophoresis and sequenced directly. Role of novel missense mutations in pathogenicity was analyzed by SIFT and sequencing NOD 2 of fifty normal controls. Clinical data of BS children diagnosed by NOD2 analysis were summarized and compared with the data of non-BS group.

(1) Twelve of eighteen suspected BS children were diagnosed as BS by NOD2 analysis, and the remaining 6 were excluded. Seven missense mutations were detected, 4 were reported before: c.1000C>T, p. Arg 334Trp; c.1001G>A, p. Arg334Gln; c.1538T>C, p. Met513Thr; c.1759C>T, p. Arg587Cys. Three novel mutations were found: c. 1147 G>C, p.Glu383Gln; c.1471A>T, p. Met491Leu; c.2006A>G, p.His669Arg. (2) Chronic symmetric arthritis and multi-joints periarticular hydatoncus, which were painless with fluctuation, were found in all 12 BS children with NOD2 mutations. Skin rash, chronic symmetric arthritis, and recurrent uveitis were identified in 7 patients. Three patients had no skin rash, while 1 had no uveitis, 1 only had symmetric arthritis and multi-joints periarticular hydatoncus. Four children inherited the disease from father. (3) Compared with other 6 non-BS children, BS children had such different clinical characteristic (P < 0.05): All the BS cases had multiple periarticular hydatoncus, which always had no persistent fever, most had no elevated CRP, while non-BS group always had no hydatoncus, most had persistent fever, all had elevated CRP.

The 12 BS children were diagnosed by NOD2 analysis; 7 missense mutations were detected, 3 were novel mutations, adding new findings to human NOD2 mutations. Although classic BS was characterized by skin rash, arthritis, and eye involvement, some presented with less than 3 of the classic features. Chronic symmetric arthritis and multi-joints periarticular hydatoncus were the most comment fetures. Comparing with non-BS group, all BS cases had multi hydatoncus surrounding multi-joints, always had no persistent fever, most had no elevated CRP. Those features may distinguish BS in clinical settings.