MUC5AC and congenital rubella syndrome: In a set of 20 articles examining the relationship between MUC5AC expression levels and CRS, 13 reported significantly elevated expression [32,40,41,44,45,58,59,60,61,62,63,64,65], 4 reported no significant difference in MUC5AC expression levels between CRS patients and control individuals [66,67,68,69], and 3 found decreased expression levels in CRS patients [37,70,71].