Phenotypic variability in Tunisian PFIC3 patients harboring a complex genotype with a differential clinical outcome of UDCA treatment.

Introduction: Progressive familial intrahepatic cholestasis type 3 (PFIC3) is a chronic autosomal recessive disorder characterized by a wide spectrum of clinical severity generally related to the degree of pathogenicity of the causal sequence variation in ABCB4 gene.

Patients And Methods: The present study reports the molecular investigation by Next Generation Sequencing (NGS) of five related patients with PFIC3 disease followed by bioinformatic analysis. A biochemical follow-up is also performed to assess the response of the ursodeoxycholic acid treatment.

Results: The molecular results revealed complex genotype in homozygous state in all patients including a pathogenic c.1436C > T (P479L) variation in the ABCB4 gene and two well-known polymorphisms, the V444A in ABCB11 gene and the D19H in the ABCG8 gene. Although the presence of the same genetic background, all patients present the disease at different ages and clinical signs with a variable degree of clinical severity at diagnosis. Additionally, a differential outcome to the treatment has been pointed out.

Conclusion: Our results provide evidence regarding the putative intervention of modifier factors in the phenotypic variability reported for the first time in the PFIC3 disease and highlight the importance of an early administration of the UDCA as a good solution to ovoid the disease progression.