Caroli syndrome: a clinical case with detailed histopathological analysis.

Herein we present a clinical case of the Caroli syndrome caused by the compound heterozygous mutation in the PKHD1 gene. Histopathological assessment of liver detected biliary cirrhosis, numerous dilated bile ducts of various sizes, hyperplastic cholangiocytes containing a large amount of acid mucopolysaccharides, decreased ß-tubulin expression and increased proliferation of cholangiocytes. A significant proportion of hepatic tissue was composed of giant cysts lined with a single layer of cholangiocytes, containing pus and bile in its lumen and surrounded by granulation tissue. An accumulation of neutrophils in the lumen of the bile ducts was observed, as well as an infiltration of the ducts and cysts surrounding connective tissue by CD4+ and to a lesser extent CD8+ lymphocytes. This may be caused by the expression of HLA-DR by cholangiocytes. Atrophy and desquamation of the epithelium of collecting tubules with the formation of microcysts were detected in the kidneys without a clinically significant loss of renal function. Morphopathogenetic mechanisms of the Caroli syndrome can be targets for a potential pathogenetic therapy and prevention of its manifestations and complications.