Criteria have been proposed by the Paris group for ‘true’ PBC/AIH overlap,272 with two out of three of (a) ALT >5 x ULN, (b) IgG >2 x ULN or positive anti-SMA and (c) liver biopsy with ‘moderate or severe periportal or periseptal lymphocytic piecemeal necrosis (interface hepatitis)’ being suggested as diagnostic of overlap in the context of a PBC diagnosis. This evidence concerns the gene SMN1 and primary biliary cholangitis.