 As a result, MWS is considered a type of periodic fever syndrome.MWS is caused by a defect in the CIAS1 gene which creates the protein cryopyrin.MWS is closely related to two other syndromes, familial cold urticaria and neonatal onset multisystem inflammatory disease—in fact, all three are related to mutations in the same gene and subsumed under the term cryopyrin-associated periodic syndromes (CAPS).