The demonstration of a heterozygous missense mutation in the MDR3 gene in a patient with ICP with no known family history of PFIC, analysed by functional studies, is a novel finding.
The patient presented at the age of 4 years with a history of severe pruritus, elevated serum gamma-glutamyltransferase and bile acid levels since several years suggesting the diagnosis of progressive familial intrahepatic cholestasis type 3 (PFIC-3) due to defects in MDR3.
Progressive familial intrahepatic cholestasis type 3 (PFIC3), for which there are limited therapeutic options, often leads to end-stage liver disease before adulthood due to impaired ABCB4-dependent phospholipid transport to bile.
Here, we report the characterization of wild type MDR3 and the Q1174E mutant, which was identified previously in a patient with progressive familial intrahepatic cholestasis type 3 (PFIC-3).
MDR3 and BSEP liver immunostaining, and analysis of biliary lipid composition should help to select PFIC candidates in whom genotyping could be proposed to confirm the diagnosis.
Functional analysis of ABCB4 mutations relates clinical outcomes of progressive familial intrahepatic cholestasis type 3 to the degree of MDR3 floppase activity.
Whereas rare mutations of this transporter were known to cause progressive familial intrahepatic cholestasis, the genome-wide association studies in Iceland find the common ABCB4 variant c.711A>T to be a general risk factor for elevated aminotransferases and higher impact variants to be potential determinants of early-onset gallstone disease, cholestasis of pregnancy, liver cirrhosis, and hepatobiliary cancer.
Adenosine triphosphate-binding cassette, subfamily B, member 4 (ABCB4) gene alterations can cause two distinct clinical entities: progressive familial intrahepatic cholestasis type 3 (PFIC3) and low phospholipid-associated cholelithiasis (LPAC).
Patients with this disease, Progressive Familial Intrahepatic Cholestasis (PFIC) type 3, have a mutation in the MDR3 gene, which is the human homologue of the murine Mdr2 gene.
Several diseases including progressive familial intrahepatic cholestasis type 3 (PFIC3), low phospholipid-associated cholelithiasis (LPAC), a subgroup of patients developing intrahepatic cholestasis of pregnancy (ICP), drug-induced liver injury and chronic cholangiopathy with biliary fibrosis and cirrhosis were attributed to ABCB4 deficiency and characterized in the past decade.
Bile acid imbalance causes progressive familial intrahepatic cholestasis type 2 (PFIC2) or type 3 (PFIC3), severe liver diseases associated with genetic defects in the biliary bile acid transporter bile salt export pump (BSEP; ABCB11) or phosphatidylcholine transporter multidrug resistance protein 3 (MDR3; ABCB4), respectively.
Among the hereditary human cholestasis, a subtype of progressive familial intrahepatic cholestasis with high gamma-glutamyltranspeptidase (GGT) serum activity shares histological, biochemical, and genetic features with mice lacking mdr2 gene expression (mdr2 -/- mice).
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.
Progressive Familial Intrahepatic Cholestasis type 3 (PFIC3) is an autosomal-recessive liver disease due to mutations in the ABCB4 gene encoding for the MDR3 protein.
Mutations in ATP-transporters ATPB81, ABCB11, and ABCB4 are responsible for progressive familial intrahepatic cholestasis (PFIC) 1, 2 and 3, and recently the gene for tight junction protein-2 (TJP2) has been linked to PFIC4.
ABCB4 deficiency, due to genetic variations, is responsible for progressive familial intrahepatic cholestasis type 3 (PFIC3) and other rare biliary diseases.