Ter Haar NM, et al. - Via a study on clinical and genetic data from 187 cases with undefined systemic autoinflammatory diseases (SAIDs) obtained from the Eurofever registry, the experts intended to define the clinical features, treatment response, and genetic findings. Out of 187, 7 subjects had a chronic disease course and 180 subjects had a recurrent disease course. Arthralgia (n=113), myalgia (n=86), abdominal pain (n=89), fatigue (n=111), malaise (n=104) and mucocutaneous manifestations (n=128) were the most generally reported symptoms. Twenty-four patients had affected relatives as well. Genetic variants were discovered in autoinflammatory genes in 15 subjects. In comparison with subjects without genetic variants, cases with genetic variants more frequently had affected relatives. Most individuals reacted well to non-steroidal anti-inflammatory drugs (NSAIDs), corticosteroids, colchicine, and anakinra. However, complete remission was seldom accomplished with NSAIDs alone. In subjects with distinctive symptoms, striking patterns were discovered. In contrast with other patients, cases with pericarditis (n=11) were older at disease onset and had fewer incidents per year. Subjects with intellectual impairment (n=8) were younger at disease onset and frequently had affected relatives. Hence, this study outlined the clinical features of a large cohort of subjects with undefined SAIDs. Moreover, cases with pericarditis and intellectual impairment seemed to include distinct subsets.