Overlap syndromes from pediatrics to adulthood

Abstract   Overlap syndromes are autoimmune conditions with mixed immunological, clinical and histological features. The most frequent overlaps are between primary biliary cirrhosis (PBC) and autoimmune hepatitis (AIH), and between AIH and sclerosing cholangitis (SC). True AIH/PBC overlap syndrome is rare and characterized by elevation of transaminases and immunoglobulin G (IgG), positive anti-smooth muscle antibodies and a liver biopsy showing interface hepatitis as well as changes typical of PBC. These patients respond to immunosuppressive treatment that must be given promptly, to avoid progression to liver failure. The so-called 'autoimmune cholangitis' defines a small group of patients with cholestatic and histological features of PBC but negative for anti-mitochondrial antibody (AMA) and positive for PBC-specific anti-nuclear antibody (ANA). The positivity for ANA in these patients is a consequence of the AMA negativity, since AMA masks ANA on immunofluorescence. These patients' clinical course and response to treatment resemble that of classical PBC. AIH/ASC overlap syndrome is characterised by elevated levels of IgG and circulating autoantibodies, including ANA, SMA and atypical perinuclear anti-neutrophil cytoplasmic antibody, in association with cholangiographic changes typical of SC. This condition affects in particular children and young adults and may represent the early stage of adult primary SC. The parenchymal liver inflammation responds satisfactorily to immunosuppression, while the bile duct damage may progress despite treatment.