Early‐onset recurrent panniculitis as a phenotype of NLRC4‐associated autoinflammatory syndrome: Characterization of pathogenicity of the p.Ser445ProNLRC4 variant

Monoallelic NLRC4 gain-of-function variants cause an inflammasomopathy with diverse clinical forms including infantile enterocolitis, recurrent macrophage activation syndrome, cold-induced urticaria-like lesions (or familial-cold autoinflammatory syndrome, FCAS4), and painful subcutaneous nodules. Here, we identified a large family with six consecutive generations affected. Genetic analyses detected the heterozygous p.Ser445Pro NLRC4 variant in three patients, which has been previously reported in a Dutch family with FCAS4. We aimed to describe the clinicopathological features and the functional consequences of the detected NLRC4 variant. Patients presented an early-onset (3 months-6 years) inflammatory disease characterized by recurrent panniculitis, fever and arthralgia. Histopathological examination showed perivascular and interstitial lymphohistiocytic infiltrates in the dermis and mixed panniculitis. Functional analysis supported the conclusion that the p.Ser445Pro NLRC4 variant leads to a constitutive activation of NLRC4-inflammasome and increased plasma levels of IL-18. Prompt recognition of early-onset panniculitis through clinicopathological examination and laboratory biomarkers may allow targeted therapies.