Centro Hospitalar de São João Porto, Porto, Portugal
Isabel Garrido, MD, Guilherme Macedo, PhD; Centro Hospitalar de São João, Porto, Porto, Portugal
Introduction: The association of antimitochondrial antibodies (AMA) with primary biliary cirrhosis (PBC) is well established. Indeed, PBC is diagnosed when there is a positive AMA test associated with elevated alkaline phosphatase levels or compatible liver histology. However, little is known about the clinical relevance of these antibodies in patients with disorders other than PBC. Thus, the purpose of this study was to review all individuals with positive AMA and to identify associated pathologic conditions. Methods: We collected data retrospectively from adult patients with AMA at a titer of 1:40 or higher between January 2010 and December 2019 at Centro Hospitalar e Universitário de São João, Portugal. Results: A total of 214 AMA-positive patients were included in the study. Most individuals were females (78.0%) and with a mean age of 58 years old (standard deviation 14 years). A diagnosis of PBC was established in 148 (69.2%) patients, 143 of whom were identified right from the beginning and 5 individuals were diagnosed during the follow-up. When analyzed the antibodies specificities, we noted that patients with PBC had positive AMA-M2 (63.5%), AMA-M4 (5.4%) and AMA-M9 (4.1%). There were also 36 (16.8%) patients with overlap syndrome with autoimmune hepatitis, 9 (4.2%) with viral hepatitis, 4 (1.9%) with drug-induced liver injury and 2 (0.9%) with autoimmune hepatitis. Beyond autoimmune hepatobiliary diseases, further 91 patients had conditions known to be associated with autoimmunity (Table 1). In 30 patients, routine liver function tests (serum transaminases, alkaline phosphatase, gamma-glutamyl transferase, bilirubin, albumin and coagulation tests) were entirely normal. Finally, AMA were found in only 7 individuals without any pathologic conditions. Discussion: Too few healthy individuals with positive AMA have been identified. Indeed, these antibodies are often associated with pathologic conditions, usually autoimmune disorders. Clinicals must be alert and maintain close monitoring on AMA-positive patients as they can develop conditions other than PBC that requires timely diagnosis and treatment during follow-up. Further studies should focus on antibodies specificities, which could provide useful diagnostic and prognostic information.
Table 1. Positive antimitochondrial antibodies and associated conditions. An individual patient may have more than one pathologic condition. PBC - primary biliary cirrhosis, AIH - autoimmune hepatitis, ALD - alcoholic liver disease, NAFLD - non-alcoholic fatty liver disease, DILI - drug-induced liver injury, SLE - systemic lupus erythematosus.
Disclosures: Isabel Garrido indicated no relevant financial relationships. Guilherme Macedo indicated no relevant financial relationships.