Long-term clinical course of patients carrying the Q703K mutation in the NLRP3 gene: a case series

BACKGROUND: Cryopyrin-associated periodic syndromes (CAPS) comprise a spectrum of apparently distinct, rare, autosomal dominant autoinflammatory disorders of increasing severity caused by NLRP3 gene mutations. The Q703K allele is a variant of unknown pathogenetic significance, and has been considered to be both a clinically unremarkable polymorphism and a low- penetrance mutation. OBJECTIVES: To analyse the long-term clinical course in a cohort of patients presenting with periodic fever attacks and carrying the Q703K mutation in the NLRP3 gene. METHODS: Seven Caucasian patients (mean age 37.3±8.5 years, 2 males and 5 females) were identified as carriers of the Q703K mutation among 71 patients with CAPS-like symptoms. RESULTS: The mean age at disease onset was 25.58±16.08 years and the mean disease duration was 12.28±8.36. The mean number of febrile episodes was 7.56±6.48 and the mean duration of fever attacks was 6.66±4.71 days. Six out of 7 patients had a low grade fever, while 1 patient had no fever episodes. All patients were characterised by symptoms consistent with recurrent inflammatory syndrome. Six patients out of 7 presented skin lesions, 4/7 arthralgia, 4/7 myalgia, 4/7 conjunctivitis, 3/7 headache. All patients also complained of severe fatigue. In 4/7 patients symptoms were triggered or worsened by generalised cold exposure. CONCLUSIONS: We suggest that patients carrying the low-penetrance Q703K mutation in the NLRP3 gene may present with FCAS-like symptoms. However, given the high frequency of healthy carriers, the role of additional, still unknown genetic and/or environmental modifiers is conceivable.