Chronic infantile neurologic, cutaneous, articular (CINCA) syndrome is characterized by fever, chronic meningitis, uveitis, sensorineural hearing loss, urticarial skin rash, and a deforming arthritis. In the CIAS1 gene of many but not all CINCA patients, disease-associated mutations have been found recently. We here describe two such patients from Germany. One of them, a 3-yr-old boy, has a 1709A→G, Y570C, mutation, which has previously been described to cause CINCA syndrome. His clinical course is very severe and no satisfying response has been achieved even with high doses of local and systemic steroids. The other patient has a somewhat milder clinical course and considerable improvement could be accomplished with moderate and low doses of steroids. In her CIAS1 gene we have found a 1043C→T, T348M, mutation, which has only been detected in Muckle–Wells syndrome before. Our results suggest that the severity of symptoms in CINCA patients may be influenced by the underlying mutation in the CIAS1 gene. Furthermore, our observations support the view that CINCA syndrome and Muckle–Wells syndrome are essentially the same disease with different degrees of severity.