CoH appearance or number in this group also remained indistinguishable from normal. All six subject patients who had CoH loss and clinical data available for review were started on treatment with UDCA. Selleckchem FK228 Posttreatment clinical follow-up was available for five of these six patients, all of whom showed normalization of abnormal serum liver

tests and diminished pruritis, results indistinguishable from our 10 PBC control patients. These results, for both subject and PBC control groups, are similar to what is expected to be the known biochemical response rate to treatment for PBC.1-3, 12 One patient each, in study and control groups, had a repeat biopsy showing “autoimmune hepatitis overlap syndrome.” Both patients were initially diagnosed with PBC based on blood test results and were treated with a favorable response for at least a year. Then, with newly rising transaminases, they underwent repeat biopsy and were found to have emergent autoimmune hepatitis overlapping with the previously assessed PBC. A recent study has shown that 2.4% of PBC patients develop an acute autoimmune hepatitis on top of their PBC.17 Nonetheless, the development of overlap syndrome after the initial biopsy finding as “minimal change” further supports that

the patient already had, at the time of first biopsy, an evolving autoimmune hepatopathy. Other concomitant autoimmune diseases in our study patients further support them as having PBC: one had a sister with PBC, three had thyroid dysfunction which is commonly associated with PBC, often predating find more the liver diagnosis18 and most strongly associated with AMA-negative PBC.19 Where did the CoH go? Prior research suggests two hypotheses. The first is that they were destroyed by immune attack, a possibility supported medchemexpress by our prior finding that they, like the bile ducts in PBC, show de novo human leukocyte antigen DR (HLA-DR) expression and may thus be targets of immune attack.4 An alternate hypothesis is that the cells lining the CoH are not destroyed, but “disappear” by undergoing hepatocellular differentiation,

as suggested by bromodeoxyuridine (BRDU), label-retaining cell assays in a murine model of acetaminophen toxicity.20 In that study, stem/progenitor cells within the CoH appeared to differentiate directly into hepatocytes without cell division. Other reports indicate that K19-positive stem/progenitor cells in the CoH can produce K19 negative/EpCAM-positive hepatocytes.7, 21 For this reason we immunostained our specimens for EpCAM as well; however, no EpCAM staining was seen in any case. This question thus remains unanswered. We conclude that diffuse CoH loss demonstrated by immunostaining for K19 can be considered a “minimal change” diagnostic biopsy feature of PBC in specimens without overt histological features classically associated with PBC.