Report Of Three Pediatric Patients With Progressive Familial Intrahepatic Cholestasis Type 3 And Review Of The Literatures

Objective Progressive familial intrahepatic cholestasis(PFIC)is a group of heterogeneous autosomal recessive disorders characterized by severe intrahepatic cholestasis.Among them,PFIC3 is caused by biallelic variants of ATP-binding cassette,subfamily B,member 4 gene(ABCB4).This paper aimed to report the clinical features and ABCB4 mutations of 3 Chinese pediatric patients with PFIC3,and to review the relevant literatures,so as to provide references for subsequent diagnostic and therapeutic study of this condition.Methods The clinical data of 3 patients with PFIC3 were collected.Genomic DNA was extracted from the peripheral blood samples of the patients and their parents.Targeted high-throughput sequencing was performed to explore the genetic cause of cholestasis,and then the positive findings were confirmed by Sanger sequencing.Moreover,the pathogenicity of the novel ABCB4 variants was predicated by using a variety of online bioinformatic tools including SIFT,Mutation Taster,PROVEAN,comparative alignment of homologous peptides,and SWISS-MODEL prediction of the molecular structures.By way of retrieving CNKI,Wanfang,VIP Database,Pubmed and other medical literature databases,a systematic literature review was conducted on all reported PFIC3 cases.Results All the 3 PFIC3 patients from 2 unrelated families had hepatosplenomegaly,with one had cirrhosis and another had died when aged 12.5 years due to liver cirrhosis and hepatoencephaly.Liver function test revealed elevated serum levels of alanine transaminase(ALT),aspartate transaminase(AST)and gamma-glutamyl transpeptidase(GGT).Besides a reportedly pathogenic variant c.602C>T(p.Thr201Met),3 novel ABCB4 variants were identified in the 3 PFIC3 patients,including a splice-site c.136-2A>G and two missense variants c.2782A>G(p.Arg928Gly)and c.1645 C >T(p.Arg549Cys),all being pathogenic/likely-pathogenic on in silico prediction.A total of 13 literatures on PFIC3 were collected,involving 55 PFIC3 patients with definite molecular diagnoses and detailed clinical data.Missense mutations were most common,accounting for 68.8%(55/80)of all the ABCB4 variants,followed by nonsense,11.3%(9/80),and then deletions,7.5%(6/80),while synonymous mutations were at the bottom of the list(1/80).For the 56 PFIC3 patients,the most common initial manifestation was pruritus(60.7%,34/56),and then came hepatomegaly(53.6% 30/56),which was followed by jaundice(48.2%,27/56).All patients(100%,56/56)showed increased GGT in laboratory examination.51.8%(29/56)of the patients had positive laboratory findings of cholestasis,but 19.6% were cholestasis-negative,and the rest 28.6%(16/56)had incomplete laboratory data.32.1%(18/56)of the PFIC3 patients had been treated with ursodeoxycholate,and among them,61.1%(11/18)got improved in response to this treatment,but 16.7%(3/18)showed ineffectiveness,while the treatment was ongoing in the other 4 patients with unclear therapeutic efffects.There were 18 patients with unknown prognosis,and 62.2%(23/37)of the rest patients had progressed to liver failure,who,at the average 8.7 years old,were waiting for or had undergone liver transplantation,with another one died when aged 8 years due to severe liver function impairment and portal hypertension.Conclusions In this study,the 3 PFIC3 patients both presented hepatosplenomegaly and high serum levels of ALT,AST and GGT.The variants c.2782A>G(p.Arg928Gly),c.1645 C >T(p.Arg549Cys)and c.136-2A >G were all novel pathogenic or likely-pathogenic ABCB4 variants.Literature review revealed that the ABCB4 variants in PFIC3 patients had remarkable heterogeneity,with missense mutations on top of the list.Clinically,pruritus was the commonest initial manifestation in PFIC3 patients,followed by hepatomegaly and jaundice.The internal medical treatment was not so promising,and ursodeoxycholate just worked well in some affected patients in short term.Liver transplantation was the most effective treatment for PFIC3 patients with liver failure.The results of this study expanded the mutation spectrum of ABCB4 gene,provided molecular evidences for the definite diagnosis,genetic counseling and prenatal diagnosis of PFIC3,improved the understanding of the clinical and molecular characteristics of this disease,and had reference value for the diagnosis and management of such patients.