Liver biopsy complicated by hemorrhage in a patient with ARC syndrome

Metabolomics and Lipidomics Reveal the Effect of Hepatic Vps33b Deficiency on Bile Acids and Lipids Metabolism

Vascular protein sorting-associated protein 33B (VPS33B) plays important roles in hepatic polarity, which directly maintains the functional structure of the liver. It has reported that VPS33B has close association with arthrogryposis, renal dysfunction and cholestasis (ARC) syndrome. Unfortunately, no further studies were conducted to reveal the role of Vps33b in the homeostasis of bile acids. In the current study, hepatic Vps33b-depleted male mice were used to investigate the metabolomics and lipidomics profiles of hepatic Vps33b deficiency based on ultrahigh-performance liquid chromatography coupled with an electrospray ionization high-resolution mass spectrometry (UHPLC-ESI-HRMS) system. Hepatic Vps33b-depleted male mice displayed cholestasis and slight liver damage with increased serum levels of ALT, AST, ALP and T-Bili compared to wild-type mice. Targeted metabolomics analysis of bile acids revealed that increased taurine-conjugated bile acids accumulated in the serum of hepatic Vps33b-depleted mice, while unconjugated bile acids were prone to decrease, accompanied by the regulation of bile acid homeostasis-related genes. In addition, lipid profiles were significantly altered with the lack of Vps33b in the liver. A variety of lipids, such as triglycerides and sphingomyelins, were significantly decreased in the liver and increased in the serum of hepatic Vps33b-depleted mice compared to those in wild-type mice. Our study demonstrated that Vps33b influences the progress of liver metabolism both in bile acid circulation and lipid metabolism, which is involved in the progression of liver cholestasis in mice.

Constipation as an Atypical Sign of ARC Syndrome - Case Report

ABSTRACT: Background: Arthrogryposis- renal tubular dysfunction - cholestasis (ARC) syndrome is a rare multisystem disorder originally described in 1973 and recently ascribed to mutation in VPS33 B whose product acts in intracellular trafficking. It exhibits wide clinical variability but the constipation isn’t a characteristic clinical sign. Case: This girl presented after birth severe contractures of legs. She was admitted at 30 days of age with poor feeding, cholestatic jaundice with normal GGT and failure to thrive . Also we have noted a severe acidosis (pH=7.2) associated with aminoaciduria and glucosuria. At second month of age the girl presented a severe ichtyosis, recurrent fever and constipation. Apart from treatment the constipation has persisted. The baby died of sepsis at 12 weeks of age. Conclusion: ARC syndrome exhibits notable clinical variability. Constipation has not been reported previously on the contrary diarrhea is a frequent clinical sign. Knowledge of this rare condition can benefit the practitioner as well as the patient.

The Role of Platelets and ε-Aminocaproic Acid in Arthrogryposis, Renal Dysfunction, and Cholestasis (ARC) Syndrome Associated Hemorrhage

Arthrogryposis, renal dysfunction, and cholestasis (ARC) syndrome is a rare disorder associated with platelet abnormalities resembling gray platelet syndrome. Affected patients have normal platelet numbers but abnormal morphology and function. Bleeding symptomatology ranges from postprocedural to spontaneous life-threatening hemorrhage. We report a patient with ARC syndrome and compound heterozygous mutations in VPS33B (vacuolar protein sorting 33B) who presented with significant bleeding requiring numerous admissions and transfusions. She was treated with prophylactic platelet transfusions and ε-aminocaproic acid. This was well-tolerated and significantly decreased transfusion requirements and admissions for bleeding. Our experience provides support for consideration of prophylactic measures in these patients as well as the possibility of using prophylaxis in related disorders.

Metazoan cell biology of the HOPS tethering complex

Membrane fusion with vacuoles, the lysosome equivalent of the yeast Saccharomyces cerevisiae, is among the best understood membrane fusion events. Our precise understanding of this fusion machinery stems from powerful genetics and elegant in vitro reconstitution assays. Central to vacuolar membrane fusion is the multi-subunit tether the HO motypic fusion and Protein Sorting (HOPS) complex, a complex of proteins that organizes other necessary components of the fusion machinery. We lack a similarly detailed molecular understanding of membrane fusion with lysosomes or lysosome-related organelles in metazoans. However, it is likely that fundamental principles of how rabs, SNAREs and HOPS tethers work to fuse membranes with lysosomes and related organelles are conserved between Saccharomyces cerevisiae and metazoans. Here, we discuss emerging differences in the coat-dependent mechanisms that govern HOPS complex subcellular distribution between Saccharomyces cerevisiae and metazoans. These differences reside upstream of the membrane fusion event. We propose that the differences in how coats segregate class C Vps/HOPS tethers to organelles and domains of metazoan cells are adaptations to complex architectures that characterize metazoan cells such as those of neuronal and epithelial tissues.

Haematological manifestations of arthrogryposis-renal dysfunction-cholestasis (ARC) syndrome: a case report

Arthrogryposis multiplex congenita, renal dysfunction, and cholestasis (ARC) syndrome is a rare, fatal, multisystem disorder. Bleeding problems, which occur spontaneously and post organ biopsies, have been reported in these patients. We report the case of an infant who had life-threatening spontaneous nasal bleeding. A detailed assessment of her platelet function and morphology is presented.

Agranular platelets as a cardinal feature of ARC syndrome

We aimed to describe abnormal platelet morphology and its clinical significance in infants who were diagnosed with arthrogryposis renal dysfunction and cholestasis (ARC) syndrome. We collected all of the cases of ARC syndrome referred to a single pediatric referral center. In all patients, platelet counts and analysis of platelet morphology were performed with peripheral blood smear specimens. Electron microscopy images were obtained to examine the ultrastructure of the platelets. Over the 12-year period, 12 cases of ARC syndrome were identified. The sex ratio (male:female) was 1:1. The median birth weight was 3.15 kg (range, 2.3 to 3.8 kg). Failure to thrive was observed in all the patients. The major cause of death was recurrent febrile illness and pneumonia. The median age at death was 8.9 months (range, 2.6 to 28.8 kg). Their median body weight at death was 3.1 kg (range, 2.6 to 6.0 kg). Close examination of their peripheral blood smear (n=11) specimens showed large, pale, agranular platelets similar to those seen in gray platelet syndrome. Electron microscopic images of the platelets (n=7) revealed a lack of alpha; granules. Agranular platelets are a common finding in ARC syndrome. Agranular platelets should be considered as a cardinal feature of ARC syndrome and can be useful as a noninvasive diagnostic marker for ARC syndrome.

Clinical and molecular genetic features of ARC syndrome

Arthrogryposis, renal dysfunction and cholestasis (ARC) syndrome (MIM 208085) is an autosomal recessive multisystem disorder that may be associated with germline VPS33B mutations. VPS33B is involved in regulation of vesicular membrane fusion by interacting with SNARE proteins, and evidence of abnormal polarised membrane protein trafficking has been reported in ARC patients. We characterised clinical and molecular features of ARC syndrome in order to identify potential genotype-phenotype correlations. The clinical phenotype of 62 ARC syndrome patients was analysed. In addition to classical features described previously, all patients had severe failure to thrive, which was not adequately explained by the degree of liver disease and 10% had structural cardiac defects. Almost half of the patients who underwent diagnostic organ biopsy (7/16) developed life-threatening haemorrhage. We found that most patients (9/11) who suffered severe haemorrhage (7 post biopsy and 4 spontaneous) had normal platelet count and morphology. Germline VPS33B mutations were detected in 28/35 families (48/62 individuals) with ARC syndrome. Several mutations were restricted to specific ethnic groups. Thus p.Arg438X mutation was common in the UK Pakistani families and haplotyping was consistent with a founder mutation with the most recent common ancestor 900-1,000 years ago. Heterozygosity was found in the VPS33B locus in some cases of ARC providing the first evidence of a possible second ARC syndrome gene. In conclusion we state that molecular diagnosis is possible for most children in whom ARC syndrome is suspected and VPS33B mutation analysis should replace organ biopsy as a first line diagnostic test for ARC syndrome.