There is growing evidence that the interplay of genetic susceptibility and environmental factors leads to primary biliary cirrhosis (PBC).
Family members of an infected individual can have a 100-fold higher risk of developing PBC.
In this study, a team of international researchers evaluated the concordance of PBC in a genetically defined population of twin sets.
They also assessed the clinical characteristics between concordant subjects.
The team identified 16 pairs of twins within a 1400-family cohort.
They evaluated the diagnosis of PBC in all individuals.
The researchers then determined the zygosity of sets reported as identical by the analysis of 2 highly variable HLA class II regions and 5 short tandem repeats.
The team found that 8 sets of twins were monozygotic.
They found that in 5 of these monozygotic twin sets, both individuals had PBC. They established that the age at onset of disease was similar in 4 of the 5 sets.
However, the team found that in the dizygotic twins, no set was found to be concordant for PBC.
Dr Carlo Selmi and colleagues concluded, "The concordance rate of PBC in identical twins is among the highest reported in autoimmunity".
"However, discordant pairs were identified".
"The data show not only the role of genetics but also emphasize that either epigenetic factors and/or environment play a critical role".