Autoinflammatory diseases (AIDs) are a recently described group of conditions caused by mutations in multiple genes that code for proteins of the innate immune system. Cryopyrin-associated periodic syndromes (CAPS) are autoinflammatory diseases comprising three clinically overlapping disorders: familial cold urticarial syndrome (FCAS), Muckle-Wells syndrome (MWS), and neonatal-onset multisystem inflammatory disease (NOMID). CAPS have been associated with gain-of-function variations in NLRP3 (NOD-like receptor family, pyrin containing domain-3). However, a new class of autoinflammatory disease resembling FCAS or MWS has been described in patients with NLRP12 mutations. Here, we report a 6-year-old boy diagnosed with AID who developed an unexpected C3 glomerulopathy during attacks and carried a novel variation in NLRP12. Following treatment with IL (interleukin) 1 targeting agents, all symptoms and inflammation resolved. This is the first case in the literature affected by both autoinflammatory disease and C3 glomerulopathy.