However, several consistent findings were found, including reports by Argüeso et al. [22] and Caffery et al. [20,21], who reported no or few differences in the expression of MUC1, MUC4, or MUC16 mRNA or protein expression between keratoconjunctivitis sicca (KCS) and control groups. Here, MUC4 is linked to Keratoconjunctivitis sicca.