Low Phospholipid-associated Cholelithiasis Research Articles

Low-Phospholipid Associated Cholelithiasis (LPAC) syndrome: A synthetic review.

Low-Phospholipid Associated Cholelithiasis (LPAC) is a genetic disease responsible for the development of intrahepatic lithiasis. It is associated with a mutation of the ABCB4 gene which codes for protein MDR3, a biliary carrier. As a nosological entity, it is defined by presence of two of the three following criteria: age less than 40 years at onset of biliary symptoms, recurrence of biliary symptoms after cholecystectomy, and intrahepatic hyperechogenic foci detected by ultrasound. While the majority of clinical forms are simple, there also exist complicated forms, involving extended intrahepatic lithiasis and its consequences: lithiasis migration, acute cholangitis, intrahepatic abscess. Chronic evolution can lead to secondary sclerosing cholangitis or secondary biliary cirrhosis. In unusual cases, degeneration into cholangiocarcinoma may occur. Treatment is built around ursodeoxycholic acid, which yields dissolution of biliary calculi. Complicated forms may call for interventional, radiological, endoscopic or surgical treatment. This synthetic review illustrates and summarizes the different aspects of this entity, from simple gallbladder lithiasis to cholangiocarcinoma, as well as secondary biliary cirrhosis requiring liver transplant, on the basis of clinical cases and the iconography of patients treated in our ward.

Clinical characteristics and genetic profiles of young and adult patients with cholestatic liver disease

heterozygous ABCB4, ABCB11 and ATP8B1 sequence variants were previously reported to be associated with low phospholipid-associated cholelithiasis, intrahepatic cholestasis of pregnancy, benign recurrent intrahepatic cholestasis and biliary lithiasis. The present study aimed to identify the presence of sequence variations in genes responsible for Mendelian liver disorders in patients with cholestatic liver disease. targeted massive parallel sequencing of a panel of genes involved in bile acid homeostasis was performed in 105 young and adult patients with cholestatic liver disease in our laboratory for molecular diagnosis. The effects of novel variants were evaluated using bioinformatics prediction tools and the Protter and Phyre2 software programs were used to create 2D, 3D topology protein modeling. Genotype-phenotype correlation was established according to molecular analysis and clinical records. twenty novel heterozygous ABCB4 sequence variations, one heterozygous ABCB4 large intragenic deletion and only one novel missense variant in ABCB11 and ATP8B1 were identified. Interestingly, heterozygous and homozygous SLC4A2 missense variants were detected in patients with low phospholipid-associated cholelithiasis. Two patients harbored heterozygous GPBAR1 variants. Common variants such as homozygous ABCB11 p.Val444Ala and heterozygous ABCG8 p.Asp19His were also identified in 12 cases. forty-eight variants were identified in five genes including ABCB4, ABCB11, ATP8B1, SLC4A2 and GPBAR1, twenty-five of which were novel. This study expands the phenotypic and mutational spectrum in genes involved in bile acid homeostasis and highlights the genetic and phenotypic heterogeneity in patients with inherited liver disorders.

The Nowhere Stone: Unusually Located Intrahepatic Calculi in a Patient with Low Phospholipid-associated Cholelithiasis Syndrome

ABSTRACTIntrahepatic calculi or hepatolithiasis is an uncommon phenomenon which is found in relatively higher rates in eastern Asian countries. Patients usually present with features of cholangitis or intrahepatic abscess and are at risk for developing cholangiocarcinoma. Correct diagnosis and management often pose challenges. A 42-year-old female presented with a history of episodic upper abdominal pain since 8 years. Initial imaging studies showed evidence of biliary calculi, but were confounding in their localization. Magnetic resonance cholangiopancreatography showed two large calculi in the right biliary system proximal to the confluence, along with choledocholithiasis. Endoscopic retrograde cholangiopancreatography and common bile duct clearance were done; however, the patient underwent hepatic sectionectomy as a curative procedure. ABCB4 mutation was detected on DNA analysis and hence aided in making the diagnosis of low phospholipid-associated cholelithiasis. Additional imaging studies are warranted in doubtful cases. Difficult accessibility of the calculi may often limit endoscopic therapeutic options and pave the way for surgical interventions. As there is an increased risk of cholangiocarcinoma in these patients, regular follow-up is essential.

ABCB4 Gene Aberrations in Human Liver Disease: An Evolving Spectrum.

ATP-binding cassette subfamily B member 4 (ABCB4) is a phospholipid translocator at the canalicular membrane of the hepatocyte, which "flops" phosphatidylcholine into bile. Dysfunction of this transporter due to ABCB4 gene variants can cause liver diseases and has been called ABCB4 deficiency. 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. LPAC and ICP are usually caused by monoallelic variants, whereas patients affected by PFIC3 are homozygous or compound heterozygous carriers of ABCB4 variants. Treatment with ursodeoxycholic acid is often effective, but as the more severe forms of ABCB4 deficiency progress, nevertheless, new diagnostic and therapeutic approaches are warranted. Current functional classifications for ABCB4 deficiency-associated mutations can guide the development of novel genotype-based targeted pharmacotherapies for these conditions. Recently, increasing evidence from genome-wide association studies is emerging on associations of ABCB4 variants with hepatobiliary malignancies.

Low phospholipid-associated cholelithiasis – An uncommon case of intrahepatic lithiasis

Low phospholipid-associated cholelithiasis – An uncommon case of intrahepatic lithiasis

Genetics of gallstone disease.

Gallstone disease (GD) belongs to the most frequent disorders in gastroenterology and causes high costs in our health-care systems. Gallstones are uncommon in children but frequent in adults, in particular in women, and are triggered by exogenous risk factors. Here, we summarize the current knowledge concerning the contribution of inherited predisposition to gallstone risk. In this review, we present the current data and recent research on the genetics of gallstone disease. Several GD-predisposing gene variants have been reported, with most prominent effects being conferred by a common variant (p.D19H) of the hepatic and intestinal cholesterol transporter ABCG5/G8. A smaller group of patients might develop gallstones primarily due low phosphatidylcholine concentrations in bile as a result of loss-of-function mutations of the ABCB4 transporter (low phospholipid-associated cholelithiasis syndrome). Regardless of the origin, the risk factors for gallstones lead to the supersaturation of bile with insoluble compounds, in particular cholesterol. As result, cholesterol stones develop and present the most frequent type of gallstones. Laparoscopic cholecystectomy with low morbidity and mortality is currently the most common and effective method for the therapy of symptomatic gallbladder stones. Gallstone disease represents a multifactorial condition and previous studies have identified the major genetic contributors to gallstone formation. The increasing knowledge about the pathomechanisms of hepatobiliary metabolism and GD as well as the identification of additional risk factors might help to overcome the current invasive therapy by specific lifestyle intervention and precise molecular treatment.

Phenotypic spectrum and diagnostic pitfalls of ABCB4 deficiency depending on age of onset.

Genetic variants in the adenosine triphosphate‐binding cassette subfamily B member 4 (ABCB4) gene, which encodes hepatocanalicular phosphatidylcholine floppase, can lead to different phenotypes, such as progressive familial intrahepatic cholestasis (PFIC) type 3, low phospholipid‐associated cholelithiasis, and intrahepatic cholestasis of pregnancy. The aim of this multicenter project was to collect information on onset and progression of this entity in different age groups and to assess the relevance of this disease for the differential diagnosis of chronic liver disease. Clinical and laboratory data of 38 patients (17 males, 21 females, from 29 families) with homozygous or (compound) heterozygous ABCB4 mutations were retrospectively collected. For further analysis, patients were grouped according to the age at clinical diagnosis of ABCB4‐associated liver disease into younger age (<18 years) or adult age (≥18 years). All 26 patients diagnosed in childhood presented with pruritus (median age 1 year). Hepatomegaly and splenomegaly were present in 85% and 96% of these patients, respectively, followed by jaundice (62%) and portal hypertension (69%). Initial symptoms preceded diagnosis by 1 year, and 13 patients received a liver transplant (median age 6.9 years). Of note, 9 patients were misdiagnosed as biliary atresia, Alagille syndrome, or PFIC type 1. In the 12 patients with diagnosis in adulthood, the clinical phenotype was generally less severe, including intrahepatic cholestasis of pregnancy, low phospholipid‐associated cholelithiasis, or (non)cirrhotic PFIC3. Conclusion: ABCB4 deficiency with onset in younger patients caused a more severe PFIC type 3 phenotype with the need for liver transplantation in half the children. Patients with milder phenotypes are often not diagnosed before adulthood. One third of the children with PFIC type 3 were initially misdiagnosed, indicating the need for better diagnostic tools and medical education. (Hepatology Communications 2018;2:504‐514)

Comparison of in silico prediction and experimental assessment of ABCB4 variants identified in patients with biliary diseases

Genetic variations of the phosphatidylcholine transporter, ABCB4 cause several biliary diseases. The large number of reported variations makes it difficult to foresee a comprehensive study of each variation. To appreciate the reliability of in silico prediction programs, 1) we confronted them with the assessment in cell models of two ABCB4 variations (E528D and P1161S) identified in patients with low phospholipid-associated cholelithiasis (LPAC); 2) we extended the confrontation to 19 variations that we had previously characterized in cellulo. Four programs (Provean, Polyphen-2, PhD-SNP and MutPred) were used to predict the degree of pathogenicity. The E528D and P1161S variants were studied in transfected HEK293 and HepG2 cells by immunofluorescence, immunoblotting and measurement of phosphatidylcholine secretion. All prediction tools qualified the P1161S variation as deleterious, but provided conflicting results for E528D. In cell models, both mutants were expressed and localized as the wild type but their activity was significantly reduced, by 48% (P1161S) and 33% (E528D). These functional defects best correlated with MutPred predictions. MutPred program also proved the most accurate to predict the pathogenicity of the 19 ABCB4 variants that we previously characterized in cell models, and the most sensitive to predict the pathogenicity of 65 additional mutations of the Human Gene Mutation Database. These results confirm the pathogenicity of E528D and P1161S variations and suggest that even a moderate decrease (by less than 50%) of phosphatidylcholine secretion can cause LPAC syndrome. They highlight the reliability of in silico prediction tools, most notably MutPred, as a first approach to predict the pathogenicity of ABCB4 variants.

Sequencing of ATP8B1, ABCB11 and ABCB4 revealed 135 genetic variants in 374 unrelated patients with suspected intrahepatic cholestasis

ATP8B1, ABCB11, and ABCB4 encode the aminophospholipidflippase familial intrahepatic cholestasis 1 (FIC1), the bile salt export pump (BSEP), and the phospholipidfloppase multidrug resistance protein 3 (MDR3), respectively, that play central roles in bile formation. Mutations in these transporters are associated with cholestatic liver diseases of varying severity ranging from milder forms like intrahepatic cholestasis of pregnancy (ICP), benign recurrent intrahepatic cholestasis (BRIC) or low phospholipid-associated cholelithiasis (LPAC) to progressive familial intrahepatic cholestasis (PFIC). At present, gene sequencing is the main method to investigate the genetic background of these different types of intrahepatic cholestasis.

ABCB4mutations underlie hormonal cholestasis but not pediatric idiopathic gallstones

To investigate the contribution of ABCB4 mutations to pediatric idiopathic gallstone disease and the potential of hormonal contraceptives to prompt clinical manifestations of multidrug resistance protein 3 deficiency. Mutational analysis of ABCB4, screening for copy number variations by multiplex ligation-dependent probe amplification, genotyping for low expression allele c.1331T>C of ABCB11 and genotyping for variation c.55G>C in ABCG8 previously associated with cholesterol gallstones in adults was performed in 35 pediatric subjects with idiopathic gallstones who fulfilled the clinical criteria for low phospholipid-associated cholelithiasis syndrome (LPAC, OMIM #600803) and in 5 young females with suspected LPAC and their families (5 probands, 15 additional family members). The probands came to medical attention for contraceptive-associated intrahepatic cholestasis. A possibly pathogenic variant of ABCB4 was found only in one of the 35 pediatric subjects with idiopathic cholesterol gallstones whereas 15 members of the studied 5 LPAC kindreds were confirmed and another one was highly suspected to carry predictably pathogenic mutations in ABCB4. Among these 16, however, none developed gallstones in childhood. In 5 index patients, all young females carrying at least one pathogenic mutation in one allele of ABCB4, manifestation of LPAC as intrahepatic cholestasis with elevated serum activity of gamma-glutamyltransferase was induced by hormonal contraceptives. Variants ABCB11 c.1331T>C and ABCG8 c.55G>C were not significantly overrepresented in the 35 examined patients with suspect LPAC. Clinical criteria for LPAC syndrome caused by mutations in ABCB4 cannot be applied to pediatric patients with idiopathic gallstones. Sexual immaturity even prevents manifestation of LPAC.

Hepatobiliary anomalies associated with ABCB4/MDR3 deficiency in adults: a pictorial essay

BackgroundABCB4/MDR3 gene variants are mostly associated with a peculiar form of cholelithiasis in European adults, currently referred to as low phospholipid-associated cholelithiasis (LPAC) syndrome.MethodsLPAC syndrome is a rare genetic disorder, characterised by the following clinical features: biliary symptoms before the age of 40, recurrence of the symptoms after cholecystectomy, and intrahepatic microlithiasis or intrahepatic hyperechogenic foci.ResultsImaging features associated with ABCB4/MDR3 mutations are not specific and correspond to a wide spectrum of biliary abnormalities. The main feature is the presence of intrahepatic lithiasis. Other uncommon presentations have been described, such as uni- or multifocal spindle-shaped dilatations of the intrahepatic bile ducts filled with gallstones, secondary sclerosing cholangitis, biliary cirrhosis, and intrahepatic cholangiocarcinoma.ConclusionThis review focuses on MR features related to ABCB4/MDR3 mutations.Main Messages• LPAC syndrome is characterised by intrahepatic microlithiasis or intrahepatic hyperechogenic foci.• Ultrasound examination is very accurate in detecting intrahepatic stones.• At MR imaging, LPAC syndrome is associated with various presentations.

Early Presentation of Low Phospholipid-Associated Cholelithiasis Syndrome

Early Presentation of Low Phospholipid-Associated Cholelithiasis Syndrome

Functional Characterization ofABCB4Mutations Found in Low Phospholipid-Associated Cholelithiasis (LPAC)

Multidrug resistance 3 (MDR3) is expressed on the canalicular membrane of the hepatocytes and plays an important role in protecting the liver from bile acids. Altered ABCB4 gene expression can lead to a rare hepatic disease, low phospholipid-associated cholelithiasis (LPAC). In this study, we characterized 3 ABCB4 mutations in LPAC patients using various in vitro assay systems. We first measured the ability of each mutant to transport paclitaxel and then the mechanisms by which these mutations might change MDR3 transport activity were determined using immunoblotting, cell surface protein biotinylation, and immunofluorescence. Through a membrane vesicular transport assay, we observed that the uptake of paclitaxel was significantly reduced in membrane vesicles expressing 2 ABCB4 mutations, F165I and S320F. Both mutants showed significantly decreased total and cell surface MDR3 expression. These data suggest two missense mutations of ABCB4 may alter function of MDR3 and ultimately can be determined as LPAC-causing mutations.

MDR3 immunostaining on frozen liver biopsy samples is not a sensitive diagnostic tool for the detection of heterozygous MDR3/ABCB4 gene mutations

Dear Editor, We read with great interest the recent article of Wendum et al. [1] describing histological lesions observed in the liver of 13 adult patients with heterozygous MDR3/ABCB4 gene mutations. They performed multidrug resistance Pglycoprotein 3 (MDR3) immunostaining on formalin-fixed paraffin-embedded sections of 11 patients and reported that the staining had a diffuse and strong canalicular pattern in patients and controls, except in one case who disclosed a faint staining. This finding suggested a lack of sensitivity of this technique for the diagnosis of MDR3/ABCB4 heterozygous mutations. Since we previously suggested that MDR3 immunostaining on frozen liver sections could be useful for the diagnosis of unexplained anicteric cholestasis in adult patients [2], we would like to contribute by providing our experience of MDR3 immunostaining realized on frozen liver biopsy sections of a new series of adult patients with MDR3/ABCB4 mutations. Between April 2007 and March 2011, 32 adult patients with unexplained anicteric cholestasis had ABCB4 gene sequencing, using polymerase chain reaction amplification and DNA sequencing of exons 2 to 28 and all splice junctions. Among these 32 patients, ten carried six different ABCB4 mutations. These ten patients (six females, 17– 72 years of age) displayed various clinical characteristics: three fulfilled the criteria for low phospholipid-associated cholelithiasis syndrome [3]; one had an anteriority of intrahepatic cholestasis of pregnancy; and six had an unexplained anicteric cholestasis—two of them with associated elevated aminotransferase level. Histopathological analysis using Picrosirius red and hematoxylin–eosin-stained liver biopsy sections showed that nine patients had portal fibrosis (three F1, four F2, one F3, and one F4 according to Ishak fibrosis score); six of them displaying a jigsaw pattern of biliary-type fibrosis. Bile duct lesions corresponding to mild cholangitis could be observed in four patients. Ductopenia, defined as a loss of more than 50 % of bile ducts, was seen in two patients. Lastly, six cases showed a mild to moderate ductular reaction. The clinicopathological features are detailed in Table 1. Frozen liver biopsies were available for 14 patients (five cases and nine controls). Immunohistochemistry was performed on 4-μm frozen sections by using MDR3 monoclonal antibody (clone P3II-26) and MRP2 antibody (clone M2III-6) as a control to check tissue immune reactivity. As shown in Fig. 1, we observed a diffuse and intense canalicular staining with MDR3 antibody, in the available frozen liver biopsies of the five patients with heterozygous ABCB4 mutations and in the nine controls. Positive canalicular staining was also observed with MRP2 antibody, confirming the immunoreactivity of our samples. These results are in contradiction with our previous report [2] in which no or faint MDR3 immunostaining was observed in frozen liver biopsies from four patients with A. Sannier (*) :M. Tepper :M. Ziol Service d’Anatomie Pathologique, GHU Paris-Seine-Saint-Denis, Hopital Jean Verdier, AP-HP, Avenue du 14 Juillet, 93143 Bondy Cedex, France e-mail: aureliesannier@free.fr

First description of ABCB4 gene deletions in familial low phospholipid-associated cholelithiasis and oral contraceptives-induced cholestasis

The wide clinical spectrum of the ABCB4 gene (ATP-binding cassette subfamily B member 4) deficiency syndromes in humans includes low phospholipid-associated cholelithiasis (LPAC), intrahepatic cholestasis of pregnancy (ICP), oral contraceptives-induced cholestasis (CIC), and progressive familial intrahepatic cholestasis type 3 (PFIC3). No ABCB4 mutations are found in a significant proportion of patients with these syndromes. In the present study, 102 unrelated adult patients with LPAC (43 patients) or CIC/ICP (59 patients) were screened for ABCB4 mutations using DNA sequencing. Heterozygous ABCB4 point or short insertion/deletion mutations were found in 37% (16/43) of the LPAC patients and in 27% (16/59) of the ICP/CIC patients. High-resolution gene dosage methodologies were used in the 70 negative patients. Here, we describe for the first time ABCB4 partial or complete heterozygous deletions in 7% (3/43) of the LPAC patients, and in 2% (1/59) of the ICP/CIC patients. Our observations urge to systematically test patients with LPAC, ICP/CIC, and also children with PFIC3 for the presence of ABCB4 deletions using molecular tools allowing detection of gross rearrangements. In clinical practice, a comprehensive ABCB4 alteration-screening algorithm will permit the use of ABCB4 genotyping to confirm the diagnosis of LPAC or ICP/CIC, and allow familial testing. An early diagnosis of these biliary diseases may be beneficial because of the preventive effect of ursodeoxycholic acid on biliary complications. Further comparative studies of patients with well-characterized genotypes (including deletions) and phenotypes will help determine whether ABCB4 mutation types influence clinical outcomes.

Maladies hépatiques liées à des anomalies héréditaires de transporteurs hépatobiliaires

The identification of biliary tranporters has enhanced our understanding of bile formation and some liver diseases. In this review, we first describe the main hepatobiliary transporters and their function. Then, some liver diseases related to mutations of biliary tranporters (FIC1/ATP8B1, BSEP/ABCB11, MDR3/ABCB4 and MRP2/ABCC2) will be described with a focus on the pathological aspects. These diseases include progressive familial intrahepatic cholestasis (PFIC), benign recurrent intrahepatic cholestasis (BRIC), intrahepatic cholestasis of pregnancy, Dubin-Johnson's syndrome and low phospholipid associated cholelithiasis (LPAC).

ABCB4 deficiency: A family saga of early onset cholelithiasis, sclerosing cholangitis and cirrhosis and a novel mutation in the ABCB4 gene

Gallstones are very common. However, there is a small group of patients with low phospholipid-associated cholelithiasis (LPAC) that is characterized by symptomatic cholelithiasis at a young age (<40 years), recurrence of biliary symptoms despite cholecystectomy and concrements or sludge in the intra- and extrahepatic biliary system. The LPAC syndrome is associated with mutations of the adenosine triphosphate-binding cassette, subfamily B, member 4 (ABCB4) gene encoding the hepatobiliary phospholipid translocator multidrug resistance protein 3 (MDR3). Impairment of MDR3 leads to a reduction of biliary phosphatidyl choline levels resulting in a lithogenic and toxic bile. This causes recurrent cholelithiasis, continuous irritations of the biliary tract with cholangitis, chronic cholestasis and even biliary cirrhosis. Here we report on a family with ABCB4 deficiency and LPAC syndrome associated with a novel mutation (c.3203T>A) in the ABCB4 gene.

Combined features of low phospholipid-associated cholelithiasis and progressive familial intrahepatic cholestasis 3

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). Based on the findings in two siblings and a review of the literature, we aimed to identify determinants of disease phenotypic traits associated with ABCB4 gene alterations. Two siblings presented, before the age of 30 years, recurrent symptomatic cholelithiasis and extensive biliary fibrosis that progressed towards portal hypertension and liver failure necessitating liver transplantation. We analysed the sequence of the ABCB4 gene and immunolocalization of the protein in the liver. Sequence analysis of ABCB11, potentially involved in similar symptoms, was also performed. Two heterozygous non-synonymous variants of ABCB4 were found in both siblings. One of them (c.959C>T; p.Ser320Phe) was previously implicated in LPAC and the second one (c.2858C>A; p.Ala953Asp) in PFIC3. Both patients were also heterozygous for the ABCB11 variant Val444Ala, which predisposes to cholestatic disorders. ABCB4 was normally detected at the canalicular membrane of hepatocytes. The review of ABCB4 gene variants reported so far shows that the vast majority of variants causing PFIC3 and LPAC are distinct. Also as a general rule, homozygous variants cause PFIC3 while heterozygous variants lead to LPAC. Combined PFIC3 and LPAC phenotype is a rare clinical event, which may be determined by the coexistence of ABCB4 variants related to both phenotypes and also potentially to the ABCB11 variant. Thus, most of the patients presenting with LPAC are not at a particular risk of developing PFIC3 features in adulthood.

Douleurs de l’hypochondre droit et fièvre

A 35-year-old woman is referred for right upper quadrant abdominal pain and fever. She had a cholecystectomy for gallstones 4 years previously. An aunt has also had a cholecystectomy. Abdominal ultrasound examination shows numerous hyperechoic foci within the liver and some "comet tail" artifacts. Because of her age (less than 40), the recurrence of biliary symptoms after cholecystectomy, her family history and the intrahepatic hyperechoic foci, the diagnosis of low phospholipid-associated cholelithiasis (LPAC) syndrome is suspected and confirmed by the demonstration of a point mutation of the ABCB4 gene. Therapy by ursodeoxycholic acid (AUDC) is started. Symptoms improve and they disappear completely within a few weeks. The cause, pathophysiology, diagnosis and treatment are reviewed.

ABCB4 sequence variations in young adults with cholesterol gallstone disease

Mutations in the gene encoding the ABCB4 [adenosine triphosphate (ATP)-binding cassette, sub-family B (MDR/TAP), member 4] transporter lower phosphatidylcholine output into bile and contribute to cholesterol gallstone formation by decreasing the solubility of cholesterol in bile. Mutations in ABCB4 have been identified in patients with low phospholipid-associated cholelithiasis. The aim of the present study was to determine the types and frequencies of ABCB4 mutations in cholecystectomized patients aged <40 years. Hundred and four patients (mean age 30.6 years, range 12-39) were included in the study and the ABCB4 gene was sequenced. The frequency of missense mutations found in the patient material was measured in 95 healthy controls. The potential functional implications of the ABCB4 missense variations were assessed by computerized analysis (BLOSUM62 and Grantham substitution matrices, polymorphism phenotyping and sorting intolerant from tolerant). One patient was heterozygous for a frameshift mutation (c.1399_1400ins10/p.Y467F fsX25). Another patient was heterozygous for a nonsense mutation (c.3136C>T/p.R1046X). These two mutations are considered detrimental to ABCB4 protein function. In addition, six missense mutations were found in the ABCB4 gene, and three of these were only present in patients. In our study, <2% of young gallstone patients were found to be heterozygous for detrimental ABCB4 mutations. The functional implication of several missense mutations remains to be clarified. Thus, mutations in the ABCB4 gene are a rare cause of gallstone disease.