Low Phospholipid-associated Cholelithiasis Syndrome Research Articles

Low phospholipid-associated cholelithiasis syndrome (LPAC), a not uncommon cause of biliary problems and hospital admissions.

Biliary diseases are a major source of morbidity and mortality for patients and a burden for the healthcare system. The genetic syndrome LPAC (low phospholipid-associated cholelithiasis) is a little known and rare entity whose treatment with bile salts avoids symptoms, admissions and the need for surgery. Our aim is to determine its incidence and characteristics in our center. Prospective study between February 2021 and September 2022. LPAC was diagnosed if (at least two): onset of biliary problems <40 years of age, recurrence of symptoms after cholecystectomy, ultrasound image of hepatolithiasis (multiple echoic foci, comet-tail images, hepatolithiasis with acoustic shadow). Demographic, clinical, genetic (analysis of MDR3 gene mutations) and ultrasound characteristics were analyzed, as well as their incidence in hospital admissions for biliary causes. 36 patients with LPAC were identified. Of these, 6 were among 237 admissions for biliary causes in the previous 9 months, with an incidence of 2.5% (95%CI 1.17-5.41). By age subgroup, the incidence was 16.7% in those admitted <40 years and 9.1% in those <50 years. Considering women only, the incidence was 21% in those admitted <40 years and 15.8% in those <50 years. All patients remained asymptomatic after treatment with ursodeoxycholic acid and there were no new admissions. LPAC syndrome is not as uncommon as it may appear, especially in women <50 years of age admitted with biliary problems. Its correct diagnosis based on simple criteria would avoid a significant number of hospital admissions and unnecessary cholecystectomies.

Tetraparesis following thoracic spine surgery in a patient with Klippel–Feil syndrome and ABCB4 mutation: a case report

BackgroundKlippel–Feil syndrome is a rare condition described in 1912 by Maurice Klippel and André Feil. It is defined as a congenital cervical fusion of at least two vertebrae, associated with a classical triad of clinical signs: short neck, low posterior hairline, and limited range of movement. However, Klippel–Feil syndrome manifests with a vast spectrum of phenotypes, ranging from no symptoms to complete triad, with or without other associated malformations. Most commonly, CCF results from sporadic mutations, even though autosomal recessive, autosomal dominant, or even X-linked inheritance can be detected. The ATP-binding cassette subfamily B member 4 is only expressed in the liver and is involved in biliary phospholipid secretion. The clinical spectrum includes various hepatobiliary pathologies, including low phospholipid-associated cholelithiasis, and has never been associated with musculoskeletal anomalies.Case presentationA 55-year-old male Caucasian patient presenting with low phospholipid-associated cholelithiasis syndrome with ATP-binding cassette subfamily B member 4 mutation and liver cirrhosis was referred to our clinic for a liver transplant. A period of 6 months before, the patient underwent a T7–T9 posterior fixation for a T8 osteoporotic fracture. Postoperatively, he was tetraparetic, whereas he was neurologically intact before the operation. At admission to our hospital, he was still tetraparetic and presented with clinical signs of cervical myelopathy. Moreover, he suffered a limitation of cervical range of motion in all directions, short neck, and low posterior hairline. Imaging showed multiple cervical and thoracic vertebral bodies fusion, as well as cervical spine stenosis. Based on the available data, we diagnosed a type 3 Klippel–Feil syndrome according to Samartzis’ classification.ConclusionsThe heterogeneity of KFS and the various potential hereditary links that are known indicate that it is important to highlight all potential cases related to known genetic defects. At present, no association between ATP-binding cassette subfamily B member 4 mutation and congenital cervical fusions has been reported. The other important clinical focus of this case is the appearance of spontaneous tetraparesis after thoracic spine surgery. This mechanism remains unclear, but considering different spinal anatomy it might have been due to difficult intubation and patient’s positioning during his previous operation.

Obeticholic acid as a second-line treatment for low phospholipid-associated cholelithiasis syndrome.

Low phospholipid-associated cholelithiasis (LPAC) syndrome is a rare genetic cause of hepatolithiasis. A pathogenic variant of the ABCB4 gene is reported in half of all patients. Ursodeoxycholic acid (UDCA) is the only drug approved. However, in some patients, UDCA fails to prevent recurrence of symptoms and complications. Experimental evidence suggests that agonists of the farnesoid-X receptor (FXR), the main transcription factor regulating ABCB4, may be beneficial in this context. To study the efficacy of obeticholic acid (OCA) in patients with LPAC syndrome with an inadequate response or intolerance to UDCA. This was a retrospective study of patients with LPAC syndrome treated with OCA, a selective FXR agonist. We reviewed the records of five OCA-treated patients (4 women; median age 29; ABCB4 variant in 4; no hepatic fibrosis). All patients received OCA at an initial dose of 5 mg daily and then 10 mg daily for a median period of 36 months in combination with UDCA (4 patients) or as a monotherapy (one patient). There were no adverse effects reported. Four patients had improvement in their symptoms - three completely and one partially. One patient had no clinical benefit. Abnormalities of blood liver tests persisted in one patient despite resolution of symptoms. Radiological signs of hepatolithiasis persisted in three of the four patients who responded clinically to OCA. These preliminary observations suggest that OCA may have the potential to effectively treat LPAC syndrome in patients with inadequate response or intolerance to UDCA. Larger studies are needed to confirm these data.

Low-phospholipid associated cholelithiasis (LPAC) syndrome: an unusual form in an elderly and overweight woman

BackgroundLow-phospholipid associated cholelithiasis (LPAC) remains an under-diagnosed condition. It can be revealed by complications such as acute cholecystitis, acute angiocholitis and acute pancreatitis. We report a case of acute pancreatitis secondary to LPAC syndrome.Case presentationA 58-year-old woman was hospitalized for recurrent biliary-type abdominal pain after cholecystectomies. The diagnosis of acute biliary pancreatitis revealing a low-phospholipid associated cholelithiasis syndrome was retained after explorations. An abdominal ultrasound performed by an expert radiologist allowed us to confirm the diagnosis of LPAC syndrome, showing a comet tail image along the intrahepatic bile ducts. Ursodeoxycholic acid was started without waiting for the result of the ABCB4 mutation. The outcome was spectacular with complete disappearance of the symptoms after the first week.ConclusionExpert ultrasound remains the key examination for the confirmation of the diagnosis of a low-phospholipid associated cholelithiasis syndrome. It should be requested at the slightest warning signs such as a young age less than 40 years and recurrence of biliary symptoms after cholecystectomy.

ABCB4 variant is associated with hepatobiliary MR abnormalities in people with low-phospholipid-associated cholelithiasis syndrome

Background & AimsThe low-phospholipid-associated cholelithiasis (LPAC) syndrome is a recently described peculiar form of cholelithiasis associated with the ATP-binding-cassette subfamily B, member 4 (ABCB4) gene deficiency. The purpose of our study was to analyse the relationship between magnetic resonance (MR) features and the genetic status of ABCB4 in people with LPAC syndrome.MethodsA total of 233 individuals with proven LPAC syndrome were enrolled between January 2003 and June 2018 in a retrospective single-centre study. Inclusion criteria included availability of clinical files, MR images, and genetic data. MR images were analysed by consensus among 3 senior radiologists blinded to the status of ABCB4 gene mutation.ResultsA total of 125 individuals (mean age at first MR imaging 40.8 years; 66% females; 48% ABCB4 variant) were included. MR abnormalities were found in 61 (49%) of the 125 individuals. Forty (67%) of the 60 individuals with an ABCB4 gene variant had MR abnormalities as compared with 21 (33%) of the 65 individuals without an ABCB4 gene variant (odds ratio [OR] 4.1, 95% CI 1.9–9.5, p = 0.0001). Compared to individuals with no variant, individuals with an ABCB4 variant were more likely to show intrahepatic macrolithiasis (56 vs. 17%; OR 6.3, 95% CI 2.6–16.2, p <0.0001), bile duct dilatation (60 vs. 18%; OR 6.5, 95% CI 2.7–16.3, p <0.0001), and at least 1 MR feature of complication (35 vs. 15%; OR 2.9, 95% CI 1.1–7.8, p <0.05).ConclusionsABCB4-related LPAC syndrome is associated with more frequent and severe hepatobiliary MR abnormalities. This finding strongly supports the major role of the ABCB4 gene in the pathogenesis of LPAC syndrome and highlights a genotype–phenotype association in this inherited disease with genetic heterogeneity.Lay summaryABCB4-related LPAC syndrome associated with an ABCB4 gene variant demonstrates more frequent and severe hepatobiliary MR abnormalities. This finding supports the major role of the ABCB4 gene in the pathogenesis of LPAC syndrome.

Should patients with symptomatic cholelithiasis before 30 years of age be tested for ABCB4 gene mutations?

Background and aims Low phospholipid-associated cholelithiasis syndrome (LPAC) is characterized by recurrent symptomatic cholelithiasis in young adults associated with ABCB4 gene mutations. Current diagnosing criteria are complex and heterogeneous, making this a largely underdiagnosed entity. Also, although recommended, genetic testing is not necessary for the diagnosis and its real advantages are not clear. The aim of our study was to explore the prevalence of ABCB4 mutations in symptomatic patients with cholelithiasis before the age of 30. Methods We conducted a multicentric prospective cohort study including patients with symptomatic cholelithiasis presenting before 30 years of age in 4 Portuguese centres between January 2017 and December 2019. ABCB4 gene was analyzed by next generation sequencing (NGS) including all exons and flanking regions. In 17/32 patients ABCB11 and ATP8B1 variants were also analyzed by NGS. Results Thirty-two patients were included (75% females, median age of symptom onset was 23 ± 5 years). We found that 8/32 (25%) patients had mutations in ABCB4 gene, 3/17 (18%) in ATP8B1 gene and 1/17 (6%) in ABCB11 gene. 44% (8/18) of patients with LPAC syndrome criteria had identified variants, while the prevalence of mutations in patients with symptoms onset before 30 as sole criteria was 29%. Conclusion Our results suggest that LPAC should be systematically suspected and investigated in patients with symptomatic cholelithiasis before age of thirty, but genetic testing should only be attempted in patients complying with the more stringent LPAC criteria.

Low phospholipid-associated cholelithiasis syndrome: A rare cause of acute pancreatitis that should not be neglected.

BACKGROUNDLow phospholipid-associated cholelithiasis (LPAC) syndrome is a very particular form of biliary lithiasis with no excess of cholesterol secretion into bile, but a decrease in phosphatidylcholine secretion, which is responsible for stones forming not only in the gallbladder, but also in the liver. LPAC syndrome may be underreported due to a lack of testing resulting from insufficient awareness among clinicians.AIMTo describe the clinical and radiological characteristics of patients with LPAC syndrome to better identify and diagnose the disease.METHODSWe prospectively evaluated all patients aged over 18 years old who were consulted or hospitalized in two hospitals in Paris, France (Bichat University Hospital and Croix-Saint-Simon Hospital) between January 1, 2017 and August 31, 2018. All patients whose profiles led to a clinical suspicion of LPAC syndrome underwent a liver ultrasound examination performed by an experienced radiologist to confirm the diagnosis of LPAC syndrome. Twenty-four patients were selected. Data about the patients’ general characteristics, their medical history, their symptoms, and their blood tests results were collected during both their initial hospitalization and follow-up. Cytolysis and cholestasis were expressed compared to the normal values (N) of serum aspartate and alanine transaminase activities, and to the normal value of alkaline phosphatase level, respectively. The subjects were systematically reevaluated and asked about their symptoms 6 mo after inclusion in the study through an in-person medical appointment or phone call. Genetic testing was not performed systematically, but according to the decision of each physician.RESULTSMost patients were young (median age of 37 years), male (58%), and not overweight (median body mass index was 24). Many had a personal history of acute pancreatitis (54%) or cholecystectomy (42%), and a family history of gallstones in first-degree relatives (30%). LPAC syndrome was identified primarily in patients with recurring biliary pain (88%) or after a new episode of acute pancreatitis (38%). When present, cytolysis and cholestasis were not severe (2.8N and 1.7N, respectively) and disappeared quickly. Interestingly, four patients from the same family were diagnosed with LPAC syndrome. At ultrasound examination, the most frequent findings in intrahepatic bile ducts were comet-tail artifacts (96%), microlithiasis (83%), and acoustic shadows (71%). Computed tomography scans and magnetic resonance imaging were performed on 15 and three patients, respectively, but microlithiasis was not detected. Complications of LPAC syndrome required hospitalizing 18 patients (75%) in a conventional care unit for a mean duration of 6.8 d. None of them died. Treatment with ursodeoxycholic acid (UDCA) was effective and well-tolerated in almost all patients (94%) with a rapid onset of action (3.4 wk). Twelve patients’ (67%) adherence to UDCA treatment was considered “good.” Five patients (36%) underwent cholecystectomy (three of them were treated both by UDCA and cholecystectomy). Despite UDCA efficacy, biliary pain recurred in five patients (28%), three of whom adhered well to treatment guidelines.CONCLUSIONLPAC syndrome is easy to diagnose and treat; therefore, it should no longer be overlooked. To increase its detection rate, all patients who experience recurrent biliary symptoms following an episode of acute pancreatitis should undergo an ultrasound examination performed by a radiologist with knowledge of the disease.

A homozygous ABCB4 mutation causing an LPAC syndrome evolves into cholangiocarcinoma

Low phospholipid-associated cholelithiasis (LPAC) is characterized by the association of ABCB4 mutations and low biliary phospholipid concentration with symptomatic and recurring cholelithiasis. In the present study, we reported a case of a 63-year-old woman, who presented a biliary pain beginning at the age of 30, recurrent after cholecystectomy, along with “comet-tail shadows” revealed by ultrasonography thus, fulfilling the diagnosis of LPAC. This disease evolved into a cholangiocarcinoma. To understand the molecular basis of this phenotype, we performed the ABCB4 gene sequencing, followed by in silico analysis and Q-RT-PCR assay. The results displayed a homozygous missense sequence variation (c.140G > A, p.Arg47Gln), predicted as pathogenic according to MutPred. Accordingly, this gave rise to a decreased hepatic ABCB4 mRNA level and structural alterations of the mutated protein. Eventually, we reported, here, the first description of an ABCB4 missense mutation (p.Arg47Gln) at homozygous state in a Tunisian LPAC syndrome. An elucidation of its functional consequences was performed. Besides, this case suggests that the delayed diagnosis of LPAC syndrome and the lack of UDCA treatment may contribute in the development of complications, such as cholangiocarcinoma.

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.

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.

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.

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

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

Cholestatic Liver Diseases from Child to Adult: The Diversity of MDR3 Disease

The phospholipidfloppase MDR3 (gene symbol: ABCB4) is expressed in the canalicular membrane of hepatocytes and mediates the biliary excretion of phosphatidylcholine, which is required for the formation of mixed micelles in bile. Several mutations of ABCB4 have been identified, which cause cholestatic liver diseases of varying severity including progressive familial intrahepatic cholestasis type 3 (PFIC-3), intrahepatic cholestasis of pregnancy (ICP) and the low phospholipid associated cholelithiasis syndrome (LPAC). Here, we report on four new (S1076N; L 23Hfs16X; c.286 + 1G > A; Q 1181E) and one known (S27G) MDR3 mutations in eight patients of three families. The patients presented with a wide spectrum of liver diseases. The clinical presentation and decisive laboratory findings or the association to a trend-setting family history led to the identification of the genetic background in these patients. Even the same mutation may be associated with varying disease progression.

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.

The Spectrum of Liver Diseases Related toABCB4Gene Mutations: Pathophysiology and Clinical Aspects

Class III multidrug resistance P-glycoproteins, Mdr2 in mice and MDR3 in human, are canalicular phospholipid translocators involved in biliary phospholipid (phosphatidylcholine) excretion. The role of an ABCB4 gene defect in liver disease has been initially proven in a subtype of progressive familial intrahepatic cholestasis called PFIC3, a severe pediatric liver disease that may require liver transplantation. Several ABCB4 mutations have been identified in children with PFIC3 and are associated with low level of phospholipids in bile leading to a high biliary cholesterol saturation index. ABCB4 mutations are associated with loss of canalicular MDR3 protein and /or loss of protein function. There is evidence that a biallelic or monoallelic ABCB4 defect causes or predisposes to several human liver diseases (PFIC3, low phospholipid associated cholelithiasis syndrome, intrahepatic cholestasis of pregnancy, drug-induced liver injury, transient neonatal cholestasis, adult biliary fibrosis, or cirrhosis). Most patients with MDR3 deficiency have a favorable outcome with ursodeoxycholic acid (UDCA) therapy, but some PFIC3 patients who do not respond to UDCA treatment still require liver transplantation. The latter should be good candidates for a targeted pharmacologic approach and/or to cell therapy in the future.

The multiple facets of ABCB4 (MDR3) deficiency

ABCB4 (MDR3), a lipid translocator, moves phosphatidylcholine from the inner to the outer leaflet of the canalicular membrane. Genetic mutations of ABCB4 lead to three distinct but related hepatobiliary diseases. Progressive familial intrahepatic cholestasis (PFIC) type 3 is a chronic cholestatic syndrome characterized by a markedly elevated gamma-glutamyltranspeptidase. Patients present with jaundice, pruritus, and hepatosplenomegaly. Periportal inflammation progresses to biliary cirrhosis and causes portal hypertension. Ursodeoxycholic acid (UDCA) normalizes liver function tests in approximately one half of treated PFIC type 3 patients. Partial responders or nonresponders eventually will require liver transplantation. Gallstone patients with ABCB4 mutations may have low phospholipid-associated cholelithiasis syndrome, characterized by cholesterol gallstones and intrahepatic microlithiasis, along with recurrent biliary symptoms, despite cholecystectomy. Patients with ABCB4 mutations also may develop intrahepatic brown pigment stones. UDCA may improve biliary symptoms even before the dissolution of stones occurs. Additional therapies such as farnesoid X receptor ligands/agonists and benzfibrates show future therapeutic promise. Intrahepatic cholestasis of pregnancy affects pregnant women with abnormal ABCB4. These women suffer from disabling pruritus and also may experience steatorrhea. Fetuses are at high risk for prematurity and stillbirths. The definitive treatment is delivery of the baby. In the interim, limited fat intake, fat-soluble vitamin supplementation, and UDCA with or without S-adenosylmethionine can provide symptomatic relief. Additional hepatobiliary diseases related to ABCB4 mutations are likely to be identified. This may result in the discovery of additional therapies for PFIC type 3, gallstones, and intrahepatic cholestasis of pregnancy.

Low phospholipid associated cholelithiasis: association with mutation in the MDR3/ABCB4 gene

Low phospholipid-associated cholelithiasis (LPAC) is characterized by the association of ABCB4 mutations and low biliary phospholipid concentration with symptomatic and recurring cholelithiasis. This syndrome is infrequent and corresponds to a peculiar small subgroup of patients with symptomatic gallstone disease. The patients with the LPAC syndrome present typically with the following main features: age less than 40 years at onset of symptoms, recurrence of biliary symptoms after cholecystectomy, intrahepatic hyperechoic foci or sludge or microlithiasis along the biliary tree. Defect in ABCB4 function causes the production of bile with low phospholipid content, increased lithogenicity and high detergent properties leading to bile duct luminal membrane injuries and resulting in cholestasis with increased serum gamma-glutamyltransferase (GGT) activity. Intrahepatic gallstones may be evidenced by ultrasonography (US), computing tomography (CT) abdominal scan or magnetic resonance cholangiopancreatography, intrahepatic hyperechogenic foci along the biliary tree may be evidenced by US, and hepatic bile composition (phospholipids) may be determined by duodenoscopy. In all cases where the ABCB4 genotyping confirms the diagnosis of LPAC syndrome in young adults, long-term curative or prophylactic therapy with ursodeoxycholic acid (UDCA) should be initiated early to prevent the occurrence or recurrence of the syndrome and its complications. Cholecystectomy is indicated in the case of symptomatic gallstones. Biliary drainage or partial hepatectomy may be indicated in the case of symptomatic intrahepatic bile duct dilatations filled with gallstones. Patients with end-stage liver disease may be candidates for liver transplantation.