Blau syndrome with a rare mutation in exon 9 of NOD2 gene

Blau syndrome with hypertension and hepatic granulomas: a case report and literature review

Background

Blau syndrome (BS) is a monogenic disorder caused by NOD2 gene variants characterized by the triad of granulomatous polyarthritis, rash, and uveitis. Atypical symptoms were recognized in one-third to one-half of individuals with BS. This study aims to describe the clinical features of BS patients with hypertension and digestive system involvement.

Methods

The complete clinical data of a BS patient complicated with hypertension and hepatic granulomas were collected and documented. We also performed a literature search to find all reported cases of BS with hypertension and digestive system involvement.

Results

We reported the case of a 19-year-old man who presented with early onset symmetric polyarthritis and hypertension at age 5 and hepatic granulomas and cirrhosis at age 19. He was diagnosed with BS by the finding of a variant of the NOD2 gene (R334W). Through the literature review, 24 patients with BS were found who were reported to have hypertension, and 38 patients were found who had different digestive system manifestations such as hepatic granulomas, hepatosplenomegaly, diverticulitis, and intestinal granuloma. Among the 38 BS patients with digestive system involvement, 14 had hepatic granulomas proven by liver biopsy.

Conclusions

Hypertension and digestive system involvement are rare manifestations of BS. Clinicians, especially rheumatologists, must be aware of atypical symptoms of BS.

Blau Syndrome Complicated by Atypical Type IIa Takayasu Arteritis

Blau syndrome (BS) is a rare, autosomal dominant monogenic autoinflammatory disease, usually presenting as a triad of symptoms (granulomatous dermatitis, uveitis, and nonerosive arthritis) and caused by gain-of-function mutations in the nucleotide oligomerization domain 2 (NOD2) gene. However, very few reports in children of copresence of BS with large vessel vasculitis exist. We hereby describe a case of BS associated with clinical features of Takayasu arteritis. An 8.5-year-old boy presented with hypertension, cardiac insufficiency, arthritis, and ocular disease. Among other investigations, he underwent cervical and chest computed tomography and computed tomography angiography scans that revealed the presence of type IIa Takayasu arteritis lesions. Genetic analysis revealed a heterozygous mutation of NOD2 gene leading to the amino acid exchange Arg-587-Cys in the NACHT domain of the NOD2 protein (R587C) as pathogenic cause of BS. He received treatment with prednisolone, methotrexate, and infliximab (antitumor necrosis factor-α) in addition to antihypertensive medication with a favorable clinical response. Cases of BS should be investigated for the coexistence of Takayasu arteritis. However, further research is required to delineate a possible common pathogenic mechanism between the two clinical entities.

Whole-exome sequencing in three children with sporadic Blau syndrome, one of them co-presenting with recurrent polyserositis

Blau syndrome (BS) is a rare, chronic autoinflammatory disease with onset before age 4 and mainly characterised by granulomatous arthritis, recurrent uveitis, and skin rash. Sporadic (also known as early-onset sarcoidosis) or familial BS is caused by gain-of-function mutations in the NOD2 gene, which encodes for a multi-task protein that plays a crucial role in the innate immune defense. We report on three Mexican patients clinically diagnosed with BS who exhibited a likely pathogenic variant in NOD2 as revealed by whole-exome sequencing (WES) and Sanger sequencing: two variants (c.1000 C > T/p.Arg334Trp and c.1538 T > C/p.Met513Thr) lie in the ATP/Mg2+ binding site, whereas the other (c.3019dupC/p.Leu1007ProfsTer2) introduces a premature stop codon disrupting the last LRR domain (LRR9) formation; all three variants are consistent with gain-of-function changes. Interestingly, all these patients presented concomitant likely pathogenic variants in other inflammatory disease-related genes, i.e. TLR10, PRR12, MEFV and/or SLC22A5. Although the clinical presentation in these patients included the BS diagnostic triad, overall it was rather heterogeneous. It is plausible that this clinical variability depends partly on the patients' genetic background as suggested by our WES results. After this molecular diagnosis and given the absence of NOD2 mutations (demonstrated in two trios) and related symptoms in the respective parents (confirmed in all trios), patients 1 and 2 were considered to have sporadic BS, while patient 3, a sporadic BS-recurrent polyserositis compound phenotype. Altogether, our observations and findings underscore the overlapping among inflammatory diseases and the importance of determining the underlying genetic cause by high-throughput methods. Likewise, this study further reinforces a pathogenic link between the here found NOD2 variants and BS and envisages potential additive effects from other loci in these, and probably other patients.