Blau syndrome (MIM 186580) is a rare granulomatous disorder inherited in an autosomal dominant manner characterized by the early appearance of granulomatous arthritis, skin rash and anterior uveitis. Missense mutations in CARD15, usually on codon 334, have been described in several families with Blau syndrome. The disorder has been described as familial; here we report the first evidence of a sporadic case of Blau syndrome in a 19 year-old man with two CARD15 mutations (R334Q and G908R). His healthy mother, father and brother did not carry the R334Q mutation, which was thus considered a neo-mutation, nor did they carry the other mutation, usually found in Crohn's disease. An extensive radiologic, histologic and laboratory evaluation and a life-long clinical follow-up is available for this patient who presented skin, joint, epididimal and eye involvement.