Study of the Malformation of Ductal Plate of the Liver in Meckel Syndrome and Review of Other Syndromes Presenting with this Anomaly

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Abstract
Meckel syndrome (MIM 249.000) is an autosomal recessive disorder with a variable spectrum of anomalies. Since the first reports of this syndrome, very broad diagnostic criteria have been proposed, but the process of defining them continues. It is probable that at least two of three manifestations, including cystic kidney dysplasia, occipital encephalocele or other anomaly of the central nervous system, and postaxial polydactyly occur in most cases. Arrest of the development of intrahepatic bile ducts at the stage of the bilaminar plate formation or ductal plate malformation is considered of high diagnostic value in Meckel syndrome, but there is no complete agreement in the literature about its occurrence. The aims of this investigation were to study the prevalence and morphologic patterns of ductal plate malformation of the liver in Meckel syndrome by evaluating the dilatation of primitive biliary structures and the increase in connective tissue of the portal tract. Archival data files from four German centers (Berlin, Freiburg, Heidelberg, Mainz) were reviewed. Liver sections of 30 well-studied fetuses with Meckel syndrome were immunostained with antibodies against cytokeratins (intermediate filaments of the cytoskeleton) and factor VIII (an endothelial cell marker) and were evaluated both qualitatively and quantitatively. Cystic kidney dysplasia, occipital encephalocele, and postaxial polydactyly were found in 100%, 90%, and 83.3% of the fetuses, respectively. Ductal plate malformation of the liver was a constant anomaly in Meckel syndrome, seen as frequently as renal lesions. We observed essentially two kinds of hepatic lesions: 23 cases showed mainly a cystic dilatation of primitive biliary structures with little portal fibrosis, while 7 cases showed mainly rings of interrupted curved lumina around a central fibrovascular axis and pronounced portal fibrosis. In these seven cases an abnormal pattern of the portal vein, with many small and closely spaced branches of the portal vein (the so-called pollard willow pattern), was also seen. With respect to other fetal developmental anomalies, no difference between the two types of lesions was found. We also provide a potentially useful comprehensive review of other genetic syndromes in which ductal plate malformations may occur.