Research Letters

Heterozygous non-sense mutation of the MDR3 gene in familial intrahepatic cholestasis of pregnancy

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific liver disease associated with a high incidence of complications in the mid and late stages of gestation. This study investigates differences in the composition of intestinal flora among pregnant women diagnosed with ICP, employing Illumina MiSeq high-throughput sequencing technology.

This case-control study obtained patient data from the hospital information system (HIS) and the laboratory information system (LIS). Fecal samples were collected from 25 pregnant women who did not undergo intestinal preparation before delivery between December 2020 and March 2021. Whole-genome analysis was performed. PCR was used to amplify the 16S rRNA V3–V4 variable region, which was then sequenced. Alpha and beta diversity were computed, and the maternal intestinal flora's abundance and composition characteristics were analyzed. Differences in intestinal flora between the two sample groups were examined.

Bacteroides and Proteobacteria exhibited positive correlations with TBIL and IBIL. Betaproteobacteria, Gammaproteobacteria, and Erysipeiotrichi showed positive correlations with TBIL, IBIL, and DBIL, while Lactobacillus, Delftia, and Odoribacter demonstrated positive correlations with ALT.

The ICP group displayed significantly higher levels of total bile acid and ALT compared to the control group. The intestinal flora composition comprised four primary phyla: Firmicutes, Actinobacteria, Bacteroidetes, and Proteobacteria. ICP patients exhibited a lower relative abundance of intestinal flora across different levels of community composition when compared to the control group. Specific correlations between certain intestinal flora and clinical liver parameters were identified.

The aim of this study was to review the literature and perform a meta-analysis to clarify the association between intrahepatic cholestasis of pregnancy and risks of long-term maternal hepatobiliary disease as well as adverse fetal outcomes including preterm birth, meconium-stained amniotic fluid, and stillbirth.

This systematic review and meta-analysis was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A comprehensive literature search was performed using Cochrane, Embase, and PubMed databases to identify observational or cohort studies comparing pregnant women with intrahepatic cholestasis of pregnancy (ICP) to pregnant women without ICP. Data from the included studies were analyzed using the Review Manager 5.4.1 software.

The meta-analysis showed a significant association between ICP and the risk of hepatobiliary diseases (pooled risk ratio [RR]: 2.81, 95% confidence interval [CI]: 2.66–2.97, p < 0.00001), hepatitis C (HC): a significant association between ICP and risk of HC (pooled RR: 4.02, 95% CI: 3.12–5.19, p < 0.00001), meconium-stained amniotic fluid (MSAF): ICP was significantly associated with an increased risk of MSAF (pooled RR: 1.91, 95% CI: 1.65–2.21, p < 0.00001), and preterm birth: the meta-analysis demonstrated a significant association between ICP and preterm birth (pooled RR: 2.11, 95% CI: 2.01–2.21, p < 0.00001).

ICP demonstrated statistically significant associations with increased risks of hepatobiliary disease, HC, MSAF, and preterm birth.

A section on the approach to diagnostic histological interpretation is the overture to this chapter on inherited and developmental disorders. This initial section is split chronologically into the early neonatal and infantile period and later childhood and adulthood, with the intention of reflecting clinical practice as closely and succinctly as possible. Disorders of the biliary tree, bile formation and secretion and hepatocyte metabolism are the core of this chapter, a merger of Chapters 3 and 4 of previous editions. Considerations on the pathogenetic and/or clinical overlap among developmental, genetic and metabolic disorders were the rationale behind this change. The complexity of hepatocyte metabolism is reflected into the myriad of related pathological conditions. Two short new paragraphs on disorders of manganese metabolism and DNA repair and nuclear envelope have been added. Recent technological advances, particularly in genomics in the last 5 years, have resulted in a plethora of new entities and changes in terminology, challenging the authors to balance detail and application to clinical practice. Tables and figures from the previous edition have been largely kept due to their quality and contemporary relevance, and updated where necessary. Liver involvement in immunodeficiency and miscellaneous disorders precede the final section on anatomical anomalies. Vascular anomalies are now included in the chapters on vascular disorders.

Serum bile acid (BA) levels testing is used for the diagnosis of intrahepatic cholestasis of pregnancy (ICP). We aimed to determine the performance of routine liver tests in the evaluation of ICP.

A retrospective cohort study conducted at a university hospital, including all pregnant women who underwent serum BA levels testing due to suspected ICP during 2007–2019. Liver tests were performed in all women including: aspartate aminotransferase (AST), alanine transaminase (ALT), alkaline phosphatase (ALK), gamma-glutamyl transferase (GGT), and total bilirubin (TB). The optimal combination of laboratory values was determined by an algorithm developed in the Python programming language.

Of 640 women who met the inclusion criteria, 22% (n = 142) were diagnosed with ICP (serum BA>10 μmol/L). A combined laboratory score of: (TB>11 μmol/L) or (ALK>255 U/L) or (GGT>32 U/L) or (AST>31 U/L), had a sensitivity of 94%, negative predictive value (NPV) of 97%, specificity of 50%, positive predictive value of 35%, and a negative likelihood ratio of 0.11 for the diagnosis of ICP. The AUC of the laboratory model alone was 0.72 (95% CI: 0.69–0.75). The addition of history of ICP to the suggested laboratory score resulted in a sensitivity of 97%, NPV of 98% and a negative likelihood ratio of 0.06. The AUC of the final model was 0.76 (95% CI: 0.72–0.79).

A combined laboratory score incorporating AST, GGT, ALK and TB was shown to reliably exclude the diagnosis of ICP. This may be particularly useful in settings with limited access to BA levels testing.

Heterozygous ABCB4 variants are not routinely tested in adults with cholestasis because of their supposed rarity and high costs.

Nineteen adult patients presenting with unexplained cholestasis, and/or recurrent gallstones were included; genotyping was not done in five due to lack of health insurance approval.

heterozygous ABCB4 variants were identified in seven patients, followed by cascade testing of 12 family members: one patient underwent liver transplantation at age 40 for end-stage liver disease; one had compensated cirrhosis; all symptomatic adults had gallstones, including four with low phospholipid-associated cholelithiasis; four had intrahepatic cholestasis of pregnancy; all children and one 54-year old female were asymptomatic. Genotype: Families A and C: c.2211G>A (p.Ala737=) combined with c.959C>T (p.Ser320Phe) in one subject; Family B: c.1130T>C (p.Ile377Thr); Family D: large deletion removing ABCB4 exons 1-4 plus ABCB1, RUNDC3B, SLC25A40, DBF4, ADAM22 exons 1-3; Family E: c.1565T>C (p.Phe522Ser) ; Family F: c.1356+2T>C combined with c.217C>G (p.Leu73Val). All patients responded to ursodeoxycholic acid.

We found ABCB4 variants in half of the adults with unexplained cholestasis and/or recurrent gallstones presenting at our center, suggesting that this condition is underdiagnosed and undertreated, with serious consequences not only for the patients and their families, but also in terms of healthcare costs.

The ATP binding cassette subfamily B member 4 (ABCB4) gene on chromosome 7 encodes the ABCB4 protein (alias multidrug resistance protein 3 [MDR3]), a P-glycoprotein in the canalicular membrane of the hepatocytes that acts as a translocator of phospholipids into bile. Several variants in ABCB4 have been shown to cause ABCB4 deficiency, accounting for a disease spectrum ranging from progressive familial cholestasis type 3 to less severe conditions like low phospholipid-associated cholelithiasis, intrahepatic cholestasis of pregnancy or drug-induced liver injury. Furthermore, whole genome sequencing has shown that ABCB4 variants are associated with an increased incidence of gallstone disease, gallbladder and bile duct carcinoma, liver cirrhosis or elevated liver function tests. Diagnosis of ABCB4 deficiency-related diseases is based on clinical presentation, serum biomarkers, imaging techniques, liver histology and genetic testing. Nevertheless, the clinical presentation can vary widely and clear genotype-phenotype correlations are currently lacking. Ursodeoxycholic acid is the most commonly used medical treatment, but its efficacy has yet to be proven in large controlled clinical studies. Future pharmacological options may include stimulation/restoration of residual function by chaperones (e.g. 4-phenyl butyric acid, curcumin) or induction of ABCB4 transcription by FXR (farnesoid X receptor) agonists or PPARα (peroxisome proliferator-activated receptor-α)-ligands/fibrates. Orthotopic liver transplantation remains the last and often only therapeutic option in cirrhotic patients with end-stage liver disease or patients with intractable pruritus.