A 4-year-old with a rash

Clinical and transcriptional response to the long-acting interleukin-1 blocker canakinumab in Blau syndrome-related uveitis

OBJECTIVE

To report on the clinical response to canakinumab in a patient with sporadic nucleotide-binding oligomerization domain-containing protein 2 (NOD-2)-associated pediatric granulomatous arthritis (Blau syndrome) and severe resistant panuveitis, and to describe gene expression profile changes throughout such treatment.

METHODS

A 4-year-old boy was diagnosed as having Blau syndrome on the basis of typical clinical features, histologic evidence of noncaseating granulomas, and a NOD2 mutation. Ocular involvement was initially controlled by topical and oral corticosteroids, but over the years visual impairment and complications, such as macular edema and retinal detachment, progressed. Ocular disease remained persistently active despite treatment with multiple different immunosuppressants; therefore, canakinumab treatment was started. Before and during the first 6 months of treatment, the gene expression profile was determined each month.

RESULTS

Canakinumab treatment was well tolerated and led to rapid quiescence of uveitis, which had been continuously active before this treatment. Gene expression profiling analysis of the patient's blood prior to initiation of interleukin-1 (IL-1) blockade revealed differential expression of 1,993 transcripts when compared to healthy controls, and among the up-regulated transcripts, pathway analysis showed that the predominant network consisted of innate immunity-related transcripts. The transcriptional signature of the patient overlapped with the transcriptional signature of patients with systemic-onset juvenile idiopathic arthritis, and canakinumab treatment led to the normalization of most of these transcriptional changes.

CONCLUSION

The pathogenesis of Blau syndrome may be mediated by IL-1, and canakinumab may be useful when this disorder is unresponsive to more conventional treatments.

Clinical features of Blau syndrome and early-onset sarcoidosis and associating CARD15/NOD2 gene mutations

Sarcoidosis is a systemic inflammatory disease clinically characterized by swelling of bilateral hilar lymph nodes and histologically defined by non-caseating epithelioid cell granulomas. Among child cases, a special subtype, called the early-onset sarcoidosis, is known to appear in children younger than 4 years of age and to be characterized by a distinct triad of skin, joint and eye disorders without pulmonary involvement. On the other hand, autosomal dominantly-transmitted disease with a characteristic features similar to those of early-onset sarcoidosis has been reported as Blau syndrome. By a linkage analysis, the responsible gene for Blau syndrome has been mapped close to the IBD (Inflammatory Bowel Disease) 1 locus. After CARD15 (NOD2), originally identified as the susceptibility gene for Crohn's disease, was also proved to be responsible for Blau syndrome, the same gene mutations have been found in sporadic early-onset sarcoidosis cases. Nod2 recognizes a signal from bacterial cell wall component in the cytoplasm of monocytic cells to activate NF-kappaB, and thus can work as an intracellular sensor of bacteria. While the loss-of-function mutations in its LRR domain are associated with Crohn's disease, Blau syndrome and early-onset sarcoidosis are autoinflammatory diseases that are caused by the gain-of-function mutations in its NOD domain.