MUC1 and pulmonary fibrosis: On the other hand, interesting insights emerged from clinical findings: patients presenting with signs and symptoms of advanced lung fibrosis (end inspiratory crackles and digital clubbing) had higher serum levels of FER and KL-6, while lower levels of FER, KL-6 and SMRP were recorded in those with extra-pulmonary signs (i.e. arthralgia/arthritis, sclerodactyly, elevated CK, myalgia, periungual erythema, mechanic’s hands).