A novel compound heterozygous mutation in ABCB4 gene in a pedigree with progressive familial intrahepatic cholestasis 3: a case report

Clinical and genetic study of ABCB4 gene-related cholestatic liver disease in China: children and adults

BACKGROUND

ABCB4 gene-related cholestatic liver diseases have a wide spectrum of clinical and genetic variations. The correlation between genotype and clinical phenotype still unclear. This study retrospectively analyzed the clinical and pathological characteristics of 23 patients with ABCB4 gene-related cholestatic liver diseases. Next-generation sequencing was used to identify the genetic causes.

RESULTS

The 23 included patients (15 children and 8 adults) were diagnosed as progressive familial intrahepatic cholestasis type 3 (PFIC3), drug-induced liver injury (DILI), cirrhosis cholestasis, cirrhosis, and mild liver fibrosis. Nineteen patients underwent liver pathological examination of the liver, exhibiting fibrosis, small bile duct hyperplasia, CK7(+), Cu(+), bile duct deletion, and cirrhosis. Thirty ABCB4 variants were identified, including 18 novel variants.

CONCLUSION

ABCB4 gene-related cholestatic liver diseases have a wide spectrum of clinical and genetic variations. Biallelic ABCB4 mutation carriers tended to severe PFIC3, which mostly occurs in children; while ABCB4 non-biallelic variants can lead to milder ICP, LACP, DILI or overlapping, mostly in adults. Thus, the ABCB4 genotype has a specific correlation with the phenotype, but there are exceptions. Non-biallelic null mutations can cause severe diseases. The mechanisms underlying this genetic phenotype require further investigation.

A novel heterozygous deletion in ABCB4 gene in a Chinese family with intrahepatic cholestasis of pregnancy, neonatal hyperbilirubinemia, and cholelithiasis: Case reports and literature review

BACKGROUND

ABCB4 gene (OMIM *171060) variant is associated with a wide clinical spectrum of hepatobiliary diseases, including familial intrahepatic cholestasis of pregnancy (ICP), progressive familial intrahepatic cholestasis type 3 (PFIC3), and neonatal hyperbilirubinemia due to impaired protection of the bile duct. The majority of reported cases, however, were missense or nonsense variants, with few deletion variant findings in the Chinese population.

METHOD

We performed whole genome sequencing and confirmed it with Sanger sequencing of the proband infant and his families. Clinical courses and laboratory results were documented and collected from the proband infant and his mother. We also reviewed other published cases related to genetic variants in ABCB4 in the Chinese population.

RESULTS

A 26-year-old Chinese female (II.2) who had recurrent intrahepatic cholestasis of pregnancy and her 49-day-old son (III.4) who had hyperbilirubinemia, both presented with extremely elevated total bile acid, cholestatic dominant pattern liver function abnormalities. They were able to stay relatively stable with mild pruritus on ursodeoxycholic acid treatment. After ruling out other possibilities, genetic sequencing revealed a diagnosis of heterozygous deletion variant NM_018849.3:c.1452_1454del (NP_061337.1:p.Thr485del) in ABCB4, which was not reported before, in the symptomatic mother (II.2), index patient (III.4), and the symptomatic grandmother (I.2). This variant resulted in clinical spectrums of ICP, neonatal hyperbilirubinemia, and cholelithiasis in our pedigree.

CONCLUSION

We reported a novel heterozygous deletion variant of the ABCB4 gene in a Chinese family, as well as a literature review of ABCB4-related disorders. We aim to facilitate healthcare professionals to better understand genetic factors as an uncommon cause of hepatobiliary diseases, as well as improve therapeutic strategies in challenging clinical situations such as pregnancy and neonatal care.

Clinical and genetic characterization of pediatric patients with progressive familial intrahepatic cholestasis type 3 (PFIC3): identification of 14 novel ABCB4 variants and review of the literatures

BACKGROUND

Progressive familial intrahepatic cholestasis type 3 (PFIC3) is an autosomal recessive disease caused by pathogenic variants of the gene ABCB4. This study aimed to investigate the ABCB4 genotypic and the clinical phenotypic features of PFIC3 patients.

METHODS

The clinical and molecular genetic data of 13 new pediatric patients with PFIC3 as well as 82 reported ones in the PubMed and CNKI databases were collected and analyzed.

RESULTS

The 13 new PFIC3 patients included six females and seven males, and the main presentations were hepatomegaly, splenomegaly, jaundice, and pruritus, as well as increased levels of gamma-glutamyl transpeptidase (GGT). Fourteen new ABCB4 variants were detected, including eight diagnosed to be likely-pathogenic and six, pathogenic. Among all the 95 PFIC3 cases, hepatomegaly was observed in 85.3% (81/95), pruritus in 67.4% (64/95), splenomegaly in 52.6% (50/95), jaundice in 48.4% (46/95), portal hypertension in 34.7% (33/95) and GGT elevation in 100% (88/88) of the patients. Positive responses at varied degrees to oral ursodeoxycholic acid (UDCA) treatment were observed in 66.1% (39/59) of the patients, among whom 38.5% (15/39) fully recovered in terms of the laboratory changes. Although the condition remained stable in 53 patients (58.9%, 53/90), the clinical outcomes were not promising in the rest 37 cases (41.1%, 37/90), including 7 died, 27 having undergone while another 3 waiting for liver transplantation. A total of 96 ABCB4 variants were detected in the 95 patients. PFIC3 patients with biallelic null variants exhibited earlier onset ages [10.5 (2, 18) vs. 19 (8, 60) months, p = 0.007], lower UDCA response rate [18.2% (2/11) vs. 77.1% (37/48), p = 0.001], and more unpromising clinical outcomes [80% (12/15) vs. 33.3% (25/75), p = 0.001], compared with those with non-biallelic null variants.

CONCLUSIONS

PFIC3 presented with hepatomegaly, pruritus, splenomegaly and jaundice with increased serum GGT level as a biochemistry hallmark. Although varying degrees of improvement in response to UDCA therapy were observed, 41.1% of PFIC3 patients exhibited unfavorable prognosis. ABCB4 genotypes of biallelic null variants were associated with severer PFIC3 phenotypes. Moreover, the 14 novel variants in this study expanded the ABCB4 mutation spectrum, and provided novel molecular biomarkers for diagnosis of PFIC3 patients.

Case Report: A rare case of young adult progressive familial intrahepatic cholestasis-type 3 with a novel heterozygous pathogenic variant of ABCB4

Progressive familial intrahepatic cholestasis type 3 (PFIC-3) is a rare autosomal recessive disorder with poor prognosis. It is caused by pathogenic variants of the ATP binding cassette subfamily B member 4 (ABCB4) gene and usually progresses from chronic cholestasis with or without jaundice to portal hypertension and end-stage liver disease within the first to second decade of life. Few reported PFIC-3 patients presented with atypical clinical symptoms, therefore, often misdiagnosed if without family history. Herein, we report a 16-year-old male who was admitted to our hospital due to acute episodes of jaundice and intense pruritus, subsequently progressed to end-stage liver disease. Laboratory examinations showed no evidence of liver injury caused by viral, autoimmune, drug or liver tumors. Ursodeoxycholic acid and dexamethasone did not relieve his symptoms and he underwent liver transplantation successfully. Targeted next-generation sequencing identified that the patient was a compound heterozygote for two missense mutations (c.959C > T/c.1429C > A) in the ABCB4 gene. The mutation c.1429C > A (p.Q477K) is a novel heterozygous mutation. We constructed a three-dimensional model of this novel pathogenic variant using the SWISS MODEL program and found that the patient's ABCB4 protein is an ATP hydrolysis deficient mutant. The postoperative pathological diagnosis showed intrahepatic cholestasis with progression to cirrhosis. Negative liver tissue immunohistochemistry of MDR3 was found in the explanted liver. The patient was diagnosed with PFIC-3, and his symptoms improved dramatically with liver transplantation. In conclusion, for young patients with acute cholestasis, pruritus, jaundice, growth retardation, and enlargement of the liver and spleen, the possibility of inherited metabolic liver diseases should be considered, detailed medical and family history should be collected, and metabolic screening tests as well as gene tests are necessary for correct diagnosis. Increasing the coverage of PFIC3 is meaningful and thus can improve the current understanding of this disease.