PRSS1 and cystic fibrosis: Mutation screening for coding regions of PRSS1, SPINK1, CFTR and the new hereditary pancreatitis-associated chymotrypsin C (CTRC) genes showed a novel variation, c.541A > G (p.S181G), in the exon 4 of PRSS1 gene and the classical CF p.F508del mutation in the CFTR. Both mutations were present in his clinically normal mother and absent in the patient's father.