A new polymorphism for the R122H mutation in hereditary pancreatitis

Background and aims-Hereditary pancreatitis (PIP) is a rare form of recurre nt acute and chronic pancreatitis. Mutations in the cationic trypsinogen (p rotease serine 1, PRSS1) gene have been identified as causing HP The R122H (previously known as R117H) mutation is the commonest and can be detected b y a single and rapid polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) based technique using the AflIII enzyme. This test however may give a false negative result in the presence of a neutral polym orphism within the enzyme recognition site. The frequency of this event was examined by sequencing studies in patients with HP and in healthy controls . Methods-Of 60 families identified by the UK and Ireland consortium of EUROP AC (European Registry for Hereditary Pancreatitis and Familial Pancreatic C ancer), 51 were screened for R122H, N29I, and A16V mutations using standard techniques, and by sequencing of all five exons of cationic trypsinogen. Results-Twelve families had the N29I mutation, one family had A16V and, on standard testing, 15 families had the R122H mutation. An additional family with the R122H mutation was found on direct sequencing. The false negative result was due to a neutral polymorphism C-->T at the third base of the cod on, not affecting the amino acid coded for, destroying the AflIII restricti on site. This polymorphism was not observed in 50DNA specimens (100 chromos omes) from controls nor from 50 individuals from PRSS1 mutation negative HP families. A novel mutation specific PCR was developed to avoid this pitfal l. Conclusions-One of the 16 families with HP and an R122H mutation contained a polymorphism affecting the AflIII restriction site. Adoption of an altern ative R122H assay is important for genetic studies in individuals with appa rent HP.