Reply to the Sannier et al. letter entitled “MDR3 immunostaining on frozen liver biopsy is not a sensitive diagnosis tool for the detection of heterozygous MDR3/ABCB4 gene mutation”

Abstract

Sir or Madam, We read with great interest the letter by Sannier et al. The data presented are consistent with our publication [1]. The authors studied a new series of adult patients with unexplained cholestasis and heterozygous MDR3/ABCB4 mutations. In five cases, a MDR3 immunostaining was performed on liver frozen sections and showed an intense canalicular staining similar to a normal staining. These results are in contradiction with their initial report that showed a faint MDR3 immunostaining in four patients with heterozygous MDR3/ABCB4 mutations [2]. This discrepancy may be explained by technical hazards or by the type of MDR3/ABCB4 mutations (indeed, the mutations were different in the two series). It could be interesting to perform MDR3 immunostainings on the formalin-fixed paraffin-embedded liver tissues in these two series that would enable a comparison with our published data which were obtained with this technique. To conclude, it seems that MDR3/ABCB4 heterozygous mutation diagnosis requires gene sequencing.