OBJECTIVE: Cryopyrin-associated periodic syndrome (CAPS) is one of the autoinflammatory disorders caused by mutations in NLRP3 gene. The over-production of interleukin (IL)-1? induced by NLRP3 gene mutations plays an important role in the pathophysiology of CAPS. We diagnosed three patients with CAPS, who were lineal family members having a novel mutation of NLRP3 gene. The objective of this report is to compare characteristics of symptoms and difference in the therapeutic responses of them, who had the same mutation. In addition, we aimed to examine the usefulness of cytokine measurement for diagnosis or determination of treatment effect of CAPS.
METHOD: A 5-year-old Japanese boy (proband), came to our hospital because of short stature, reached the diagnosis of Muckle-Wells syndrome (MWS) which is one of the phenotype of CAPS. It is due to a mutation in NLRP3 gene, which had not been reported (p.G328E, c.G983A). His mother and grandmother harbored the same mutation of NLRP3. We measured serum concentrations of cytokines in the proband assessed by flow-cytometric bead array. All of them had episodic skin eruptions with conjunctivitis, hearing loss, and arthralgia, but not periodic fever, cold-triggered episodes, and chronic aseptic meningitis. The increase of serum C-reactive protein level and erythrocyte sedimentation rate was observed during symptomatic period in all the three people.
RESULT: Canakinumab therapy led to a prompt relief of symptoms and normalized laboratory data in all patients. Audiograms demonstrated an improved hearing level in the proband, but not two others despite of the same mutation. All cytokines did not show any characteristic findings. Sensorineural hearing loss and itchless rash but not serum cytokine profile deserved attention to the diagnosis and treatment start of MWS.
CONCLUSION: Early intervention of IL-1? blockade may reduce the chance of complete deafness in patients with MWS.