A novel mutation in VPS33B gene causing a milder ARC syndrome phenotype with prolonged survival

Molecular mechanisms and genetic factors contributing to the developmental dysplasia of the hip

The most prevalent hip disease in neonates is developmental dysplasia of the hip (DDH). A timely and accurate diagnosis is required to provide the most effective treatment for pediatric patients with DDH. Heredity and gene variation have been the subject of increased attention and research worldwide as one of the factors contributing to the pathogenesis of DDH. Genome-wide association studies (GWAS), genome-wide linkage analyses (GWLA), and exome sequencing (ES) have identified variants in numerous genes and single-nucleotide polymorphisms (SNPs) as being associated with susceptibility to DDH in sporadic and DDH family patients. Furthermore, the DDH phenotype can be observed in animal models that exhibit susceptibility genes or loci, including variants in CX3CR1, KANSL1, and GDF5. The dentification of noncoding RNAs and de novo gene variants in patients with DDH-related syndrome has enhanced our understanding of the genes implicated in DDH. This article reviews the most recent molecular mechanisms and genetic factors that contribute to DDH.

Arthrogryposis, renal dysfunction, cholestasis syndrome with a novel mutation in two siblings

This current case series adds to the spectrum of Arthrogryposis renal dysfunction cholestasis (ARC)-associated variants. Increased awareness and early genetic testing for ARC are suggested in cases with failure to thrive, renal tubular dysfunction, and rickets, even when the degree of cholestasis is mild. Prompt identification and intervention may improve the quality of life.

Arthrogryposis, renal dysfunction, cholestasis syndrome in a neonate: an uncommon association of common problems

A male infant born out of non-consanguineous marriage to a primigravida presented to us as his third hospitalisation with ichthyotic lesions all over the body, cholestatic jaundice, multiple joint contractures and a history of recurrent sepsis. Blood and urine investigations revealed Fanconi syndrome, hypothyroidism and direct hyperbilirubinaemia with elevated liver enzymes and normal gamma glutamyl transpeptidase levels. The combination of arthrogryposis, renal dysfunction and cholestasis led to the suspicion of arthrogryposis, renal tubular dysfunction, cholestasis (ARC) syndrome, which was then proved by genetic testing. The baby was managed conservatively with respiratory support, antibiotics, multivitamins, levothyroxine and other supportive measures but succumbed to the illness on day 15 of hospitalisation. Genetic analysis using next-generation sequencing was confirmatory of a homozygous mutation in VIPAS39 gene leading to ARC syndrome type 2 in the present case. Genetic counselling was provided and prenatal testing was advised to the parents for future pregnancies.

Congenital Ichthyosis: Clinical and Genetic Characteristics of the Disease

Congenital ichthyosis is a group (almost 100 clinical variants) of rare genetic skin diseases caused by pathogenic changes in more than 50 genes. Clinical features of ichthyosis, regardless of its genotype, are dry skin, peeling, hyperkeratosis frequently accompanied with erythroderma. These patients have extremely low quality of life due to changes in appearance, discomfort due to itching and functional limitations (pain during walking, impaired hands motor skills and functions due to hyperkeratosis foci in functionally relevant areas), as well as impaired functions of various organs and systems in syndromic forms of disease. Patients need daily skin care and systemic medications. By now, there is no definitive treatment for ichthyosis. Diagnostic difficulties in determining the clinical forms of congenital ichthyosis are associated with their clinical heterogeneity and with similarity in external manifestations. Difficulties in differential diagnosis with other dermatoses are particularly crucial in case of syndromic forms of disease. This review presents the modern classification of ichthyoses, provides data on disease clinical and genetic variants, diagnostic algorithms, treatment methods for patients with this severe disease.

Two novel mutations in the VPS33B gene in a Chinese patient with arthrogryposis, renal dysfunction and cholestasis syndrome 1: A case report

BACKGROUND

The VPS33B (OMIM: 608552) gene is located on chromosome 15q26.1. We found a female infant with autosomal recessive arthrogryposis, renal dysfunction and cholestasis syndrome 1 (ARCS1) caused by mutation in VPS33B. The child was diagnosed with ARCS1 (OMIM: 208085) after the whole exome sequencing revealed two heterozygous mutations (c.96+1G>C, c.242delT) in the VPS33B gene.

CASE SUMMARY

We report a Chinese female infant with neonatal cholestasis disorder, who was eventually diagnosed with ARCS1 by genetic analysis. Genetic testing revealed two new mutations (c.96+1G>C and c.242delT) in VPS33B, which is the causal gene. The patient was compound heterozygous, and her parents were both heterozygous.

CONCLUSION

This study extends the mutational spectrum of the VPS33B gene to provide a molecular basis for the etiological diagnosis of ARCS1 and for genetic counseling of the family.

Platelet VPS16B is dependent on VPS33B expression, as determined in two siblings with arthrogryposis, renal dysfunction, and cholestasis syndrome

BACKGROUND

Platelet α-granule biogenesis in precursor megakaryocytes is critically dependent on VPS33B and VPS16B, as demonstrated by the platelet α-granule deficiency seen in the rare multisystem disorder arthrogryposis, renal dysfunction, and cholestasis (ARC) syndrome associated with biallelic pathogenic variants in VPS33B and VIPAS39 (encoding VPS16B). VPS33B and VPS16B are ubiquitously expressed proteins that are known to interact and play key roles in protein sorting and trafficking between subcellular locations. However, there remain significant gaps in our knowledge of the nature of these interactions in primary cells from patients with ARC syndrome.

OBJECTIVES

To use primary cells from patients with ARC syndrome to better understand the interactions and roles of VPS33B and VPS16B in platelets and precursor megakaryocytes.

PATIENTS/METHODS

The proband and his male sibling were clinically suspected to have ARC syndrome. Confirmatory genetic testing and platelet phenotyping, including electron microscopy and protein expression analysis, was performed with consent in a research setting.

RESULTS

We describe the first case of ARC syndrome identified in Costa Rica, associated with a novel homozygous nonsense VPS33B variant that is linked with loss of expression of both VPS33B and VPS16B in platelets.

CONCLUSION

These results indicate that stable expression of VPS16B in platelets, their precursor megakaryocytes, and other cells is dependent on VPS33B. We suggest that systematic evaluation of primary cells from patients with a range of VPS33B and VIPAS39 variants would help to elucidate the interactions and functions of these proteins.

One case of arthrogryposis-renal dysfunction-cholestasis (ARC) syndrome featuring an incomplete and mild phenotype

Background

Arthrogryposis-renal dysfunction-cholestasis (ARC) syndrome is a rare disease with a high mortality rate caused by VPS33B or VIPAS39 mutations. ARC syndrome typically presents with arthrogryposis, renal tubular leak and neonatal cholestatic jaundice, and most patients with this disease do not survive beyond one year.

Case presentation

Here, we report the case of a 13-year-old girl with ARC featuring an incomplete and mild phenotype with novel compound heterozygous mutations of VPS33B. The patient presented with arthrogryposis (claw-shaped limbs), ichthyosis, jaundice, and pruritus. Laboratory tests revealed highly evaluated levels of total bilirubin (TB), direct bilirubin (DB), and total bile acid (TBA) as well as normal levels of gamma-glutamyltransferase (GGT). However, signs of renal dysfunction, as well as other manifestations of ARC syndrome, including nervous system abnormalities, deafness, and failure to thrive, were not observed. The patient’s clinical symptoms of jaundice and pruritus were significantly alleviated by administration of ursodeoxycholic acid. Whole-exome sequencing (WES) revealed novel compound heterozygous mutations of VPS33B, c.1081 C > T (p.Q361X,257)/c.244 T > C (p.C82R). Both variants were predicted to be pathogenic in silico and have never been reported previously. To date, the patients’ cholestatic jaundice has been well controlled with continuous treatment of ursodeoxycholic acid.

Conclusions

We report the case of a Chinese female with ARC including novel compound heterozygous mutations of VPS33B and an incomplete and mild phenotype. Early diagnosis and suitable symptomatic therapies are critical for the management of ARC patients with mild manifestations and prolonged lifespan.

Mild Phenotype of Arthrogryposis, Renal Dysfunction, and Cholestasis Syndrome 1 Caused by a Novel VPS33B Variant

The arthrogryposis, renal dysfunction, and cholestasis syndrome (ARCS) is an autosomal recessive multisystem disease caused by variants in VPS33B or VIPAS39. The classical presentation includes congenital joint contractures, renal tubular dysfunction, cholestasis, and early death. Additional features include ichthyosis, central nervous system malformations, platelet dysfunction, and severe failure to thrive. We studied three patients with cholestasis, increased aminotransferases, normal gamma-glutamyl transferase, and developmental and language delay. Whole exome sequencing analysis identified VPS33B variants in all patients: patients 1 and 2 presented a novel homozygous variant at position c.1148T>A. p.(Ile383Asn), and patient 3 was compound heterozygous for the same c.1148T>A. variant, in addition to the c.940-2A>G. variant. ARCS is compatible with the symptomatology presented by the studied patients. However, most patients that have been described in the literature with ARCS had severe failure to thrive and died in the first 6 months of life. The three patients studied here have a mild ARCS phenotype with prolonged survival. Consequently, we believe that the molecular analysis of the VPS33B and VIPAS39 should be considered in patients with normal gamma-glutamyl transferase cholestasis.

Novel gene mutations in three Japanese patients with ARC syndrome associated mild phenotypes: a case series

Background

Arthrogryposis, renal dysfunction, and cholestasis syndrome (ARCS) is a rare autosomal recessive disorder caused by mutations in VPS33B (ARCS1) and VIPAS39 (ARCS2). As per literature, most patients with ARCS died of persistent infections and bleeding by the age of 1 year. We report the first Japanese cases with ARCS1 and ARCS2 who presented with mild phenotypes and were diagnosed via genetic testing.

Case presentation

Case 1: A 6-year-old boy born to nonconsanguineous Japanese parents presented with jaundice and normal serum gamma-glutamyl transferase (GGT) levels, proteinuria, bilateral nerve deafness, motor delay, failure to thrive, and persistent pruritus. After cochlear implantation for deafness at the age of 2 years, despite a normal platelet count and prothrombin time-international normalized ratio, the patient presented with persistent bleeding that required hematoma removal. Although he did not show any obvious signs of arthrogryposis, he was suspected to have ARCS based on other symptoms. Compound heterozygous mutations in VPS33B were identified using targeted next-generation sequencing (NGS), which resulted in no protein expression. Case 2: A 7-month-old boy, the younger brother of case 1, presented with bilateral deafness, renal tubular dysfunction, failure to thrive, and mild cholestasis. He had the same mutations that were identified in his brother’s VPS33B. Case 3: A 24-year-old man born to nonconsanguineous Japanese parents was suspected to have progressive familial intrahepatic cholestasis 1 (PFIC1) in his childhood on the basis of low GGT cholestasis, renal tubular dysfunction, sensory deafness, mental retardation, and persistent itching. A liver biopsy performed at the age of 16 years showed findings that were consistent with PFIC1. He developed anemia owing to intraperitoneal hemorrhage from a peripheral intrahepatic artery the day after the biopsy, and transcatheter arterial embolization was required. ARCS2 was diagnosed using targeted NGS, which identified novel compound heterozygous mutations in VIPAS39.

Conclusions

The first Japanese cases of ARCS1 and ARCS2 diagnosed using genetic tests were reported in this study. These cases are milder than those previously reported. For patients with ARCS, invasive procedures should be performed with meticulous care to prevent bleeding.

Two novel mutations in VPS33B gene cause a milder ARC syndrome with prolonged survival in a 12-year-old patient: Case report

Arthrogryposis-renal dysfunction-cholestasis (ARC) syndrome is a rare autosomal recessive disease caused by VPS33B and VIPAR gene mutations. The main clinical manifestations are congenital joint contracture, renal dysfunction mainly characterized by distal renal tubular dysfunction, and low glutamyltransferase cholestasis. Most patients with ARC die within 2 years of birth. Here, we report the case of a 12-year-old girl with an ARC phenotype who experienced long-term survival with only mild clinical symptoms. We detected two new heterozygous mutation sites of the VPS33B gene in this child, c.1081C > T (p.GLN361X, 257) and c.244T > C (p.Cys82Arg), through the gene detection technique; the tertiary structure of the protein was predicted by using the SWISS-model. We further reviewed the literature and summarized the clinical manifestations and gene loci of 19 ARC syndrome patients with long-term survival reported so far.

A New Aberration in the VPS33B Gene Leads to Full-Symptom ARCS1

BACKGROUND ARCS1 is an acronym for arthrogryposis, renal dysfunction, and cholestasis. It is a congenital malfunction with autosomal recessive inheritance, and, unfortunately, its prognosis is still poor. It is believed that VPS33B is altered in 75% of cases and that the VIPAR gene is altered in approximately 25% of them. CASE REPORT An affected child was born from the first pregnancy of 26-year-old mother and a 30-year-old father with no previous medical history and no genetic conditions. The first clinical symptoms were observed at the end of the child's second week of life. The mother reported the child has decreasing body weight and loss of appetite. After admission to the ward, the child was apathetic and sleepy. Symptoms of conjunctivitis, pale and dry skin, and mild face and mild body dysmorphia were observed. CONCLUSIONS Laboratory tests revealed proteinuria of up to 1.36 g/l and glycosuria of up to 28 mmol/l, as well as fluctuating metabolic acidosis. The bilirubin level reached 6.62 mg/dl, along with alkaline phosphatase at 470 U/l. Moreover, hypothyroidism with TSH at 16.71 uU/ml was observed. Because of the co-occurrence of cholestasis and renal dysfunction, molecular testing was done. The 17th exon of VPS33B was sequenced by Sanger DNA sequencing method. To the best of our knowledge, this is the first report of homozygotic mutation c.1235_1236delinsG (p.Pro412ArgfsTer7) in the VPS33B gene. The risk of transfer of the mutation to future descendants was calculated as 25%. Due to the wide landscape of molecular alternation in the 17th exon of the VPS33B gene, we propose using Sanger whole-exon sequencing as a first-choice diagnostic test.

A Novel Mutation of VPS33B Gene Associated with Incomplete Arthrogryposis-Renal Dysfunction-Cholestasis Phenotype

Arthrogryposis-renal dysfunction-cholestasis (ARC) syndrome is an autosomal recessive disorder caused by mutations of the VPS33B encoding the vacuolar protein sorting 33B (VPS33B), which is involved in the intracellular protein sorting and vesicular trafficking. We report a rare case of ARC syndrome without arthrogryposis caused by a novel mutation of VPS33B. A female patient of Greek origin presented on the 14^th day of life with renal tubular acidosis, Fanconi syndrome, nephrogenic diabetes insipidus, and cholestasis with normal gamma-glutamyl transpeptidase, without arthrogryposis and dysmorphic features. She was born to apparently healthy, nonconsanguineous parents. Additional features included dry and scaling skin, generalized hypotonia, hypoplastic corpus callosum, neurodevelopmental delay, failure to thrive, short stature, recurrent febrile episodes with and without infections, and gastrointestinal bleeding. DNA testing revealed that the patient was homozygous for the novel c.1098_1099delTG (p.Glu367Alafs∗17) mutation of exon 14 of VPS33B gene (NM_018668) on chromosome 15q26.1, leading to a nonsense frameshift variant of VPS33B with premature termination of translation. Her parents were heterozygous for the same VPS33B mutation. The prognosis was predictably poor in the context of the intractable polyuria necessitating long-term parenteral fluid administration via indwelling central catheter leading to catheter-related sepsis, to which she eventually succumbed at the age of 7 months. This is the first published VPS33B mutation in an ARC patient of Greek origin. The current case adds to the spectrum of ARC-associated VPS33B mutations and provides evidence supporting the existence of incomplete ARC phenotype. Increased awareness and early genetic testing for ARC are suggested in cases with isolated cholestasis and/or renal tubular dysfunction, even in the absence of arthrogryposis.