Tricho-hepato-enteric syndrome (THE-S): two cases and review of the literature

Trichohepatoenteric syndrome and cytomegalovirus infection: Case report and literature summary

Trichohepatoenteric syndrome is a rare autosomal recessive genetic disease caused by TTC37 (also known as SKIC3) or SKIV2L gene variant. We present a severely affected 2-month-old male infant with recurrent fever and unexplained diarrhea. Additionally, clinical data of 11 patients with trichohepatoenteric syndrome in China from 1 to 60 days of onset was presented. The infant's condition was not substantially relieved after cefotaxime sulbactam and meropenem treatment. Whole-exome sequencing revealed compound heterozygous variants (c.1708C>T and c.3342-9T>G) in TTC37 of the child whose parents were heterozygous carriers of the corresponding locus. The c.3342-9T>G variant originated from his mother and was reported for the first time. Combined with the clinical manifestations, the infant was diagnosed with trichohepatoenteric syndrome and treated with ganciclovir antiviral, intravenous nutritional support, and liver function protection. The infant was discharged with no fever and high stool frequency, but his condition improved. Therefore, trichohepatoenteric syndrome should be considered for recurrent fever and unexplained diarrhea.

Diet management in congenital diarrheas and enteropathies - general concepts and disease-specific approach, a narrative review

Congenital diarrheas and enteropathies (CODE) are a group of rare, heterogenous, monogenic disorders that lead to chronic diarrhea in infancy. Definitive treatment is rarely available, and supportive treatment is the mainstay. Nutritional management in the form of either specialized formulas, restrictive diet, or parenteral nutrition support in CODE with poor enteral tolerance is the cornerstone of CODE treatment and long-term growth. The evidence to support the use of specific diet regimens and nutritional approaches in most CODE disorders is limited due to the rarity of these diseases and the scant published clinical experience. The goal of this review was to create a comprehensive guide for nutritional management in CODE, based on the currently available literature, disease mechanism, and the PediCODE group experience. Enteral diet management in CODE can be divided into 3 distinct conceptual frameworks: nutrient elimination, nutrient supplementation, and generalized nutrient restriction. Response to nutrient elimination or supplementation can lead to resolution or significant improvement in the chronic diarrhea of CODE and resumption of normal growth. This pattern can be seen in CODE due to carbohydrate malabsorption, defects in fat absorption, and occasionally in electrolyte transport defects. In contrast, general diet restriction is mainly supportive. However, occasionally it allows parenteral nutrition weaning or reduction over time, mainly in enteroendocrine defects and rarely in epithelial trafficking and polarity defects. Further research is required to better elucidate the role of diet in the treatment of CODE and the appropriate diet management for each disease.

SKI complex: A multifaceted cytoplasmic RNA exosome cofactor in mRNA metabolism with links to disease, developmental processes, and antiviral responses

RNA stability and quality control are integral parts of gene expression regulation. A key factor shaping eukaryotic transcriptomes, mainly via 3'-5' exoribonucleolytic trimming or degradation of diverse transcripts in nuclear and cytoplasmic compartments, is the RNA exosome. Precise exosome targeting to various RNA molecules requires strict collaboration with specialized auxiliary factors, which facilitate interactions with its substrates. The predominant class of cytoplasmic RNA targeted by the exosome are protein-coding transcripts, which are carefully scrutinized for errors during translation. Normal, functional mRNAs are turned over following protein synthesis by the exosome or by Xrn1 5'-3'-exonuclease, acting in concert with Dcp1/2 decapping complex. In turn, aberrant transcripts are eliminated by dedicated surveillance pathways, triggered whenever ribosome translocation is impaired. Cytoplasmic 3'-5' mRNA decay and surveillance are dependent on the tight cooperation between the exosome and its evolutionary conserved co-factor-the SKI (superkiller) complex (SKIc). Here, we summarize recent findings from structural, biochemical, and functional studies of SKIc roles in controlling cytoplasmic RNA metabolism, including links to various cellular processes. Mechanism of SKIc action is illuminated by presentation of its spatial structure and details of its interactions with exosome and ribosome. Furthermore, contribution of SKIc and exosome to various mRNA decay pathways, usually converging on recycling of ribosomal subunits, is delineated. A crucial physiological role of SKIc is emphasized by describing association between its dysfunction and devastating human disease-a trichohepatoenteric syndrome (THES). Eventually, we discuss SKIc functions in the regulation of antiviral defense systems, cell signaling and developmental transitions, emerging from interdisciplinary investigations. This article is categorized under: RNA Turnover and Surveillance > Turnover/Surveillance Mechanisms RNA Turnover and Surveillance > Regulation of RNA Stability RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes.

Targeted Gene Sanger Sequencing Should Remain the First-Tier Genetic Test for Children Suspected to Have the Five Common X-Linked Inborn Errors of Immunity

To address inborn errors of immunity (IEI) which were underdiagnosed in resource-limited regions, our centre developed and offered free genetic testing for the most common IEI by Sanger sequencing (SS) since 2001. With the establishment of The Asian Primary Immunodeficiency (APID) Network in 2009, the awareness and definitive diagnosis of IEI were further improved with collaboration among centres caring for IEI patients from East and Southeast Asia. We also started to use whole exome sequencing (WES) for undiagnosed cases and further extended our collaboration with centres from South Asia and Africa. With the increased use of Next Generation Sequencing (NGS), we have shifted our diagnostic practice from SS to WES. However, SS was still one of the key diagnostic tools for IEI for the past two decades. Our centre has performed 2,024 IEI SS genetic tests, with in-house protocol designed specifically for 84 genes, in 1,376 patients with 744 identified to have disease-causing mutations (54.1%). The high diagnostic rate after just one round of targeted gene SS for each of the 5 common IEI (X-linked agammaglobulinemia (XLA) 77.4%, Wiskott–Aldrich syndrome (WAS) 69.2%, X-linked chronic granulomatous disease (XCGD) 59.5%, X-linked severe combined immunodeficiency (XSCID) 51.1%, and X-linked hyper-IgM syndrome (HIGM1) 58.1%) demonstrated targeted gene SS should remain the first-tier genetic test for the 5 common X-linked IEI.

Novel TTC37 mutations in a patient with Trichohepatoenteric syndrome: a case report and literature review

BACKGROUND

Trichohepatoenteric syndrome (THES) is a rare autosomal recessive genetic disease caused by pathogenic mutations in TTC37 or SKIV2L gene. The presentation is variable, including intractable diarrhea, woolly hair abnormality, immune dysfunction, intrauterine growth restriction (IUGR), facial dysmorphism, and sometimes liver and skin abnormalities. Although four Chinese children affected with THES syndrome 1 have been described in Singapore, Taiwan (China) and Malaysia, to our knowledge, this is the first report of a patient with THES in Mainland China, harboring classical platelets features, clinical course, and novel mutations in TTC37 gene.

CASE DESCRIPTION

The male infant had symmetrical IUGR, and was born at 37⁺¹ weeks with a birth weight of 1,480 g. He presented with feeding difficulties and vomiting from the 12^th day after birth during the stay in neonatal intensive care unit, and had excessive diarrhea from the 21st day after birth. From the 35^th day after birth, even slightly hypotonic oral rehydration solution caused watery stools. The blood glucose level was lower than 3.3 mmol/L even when the glucose infusion rate was up to 14 mg/kg/min on the parenteral alone, which has not been reported in previous literature. Normal α-granules were observed occasionally in THES platelets. Whole-exome sequencing analysis identified compound heterozygous mutations (c.4130C > G: p.S1377X) and (Exon11-13 del) in the TTC37 gene, which had been inherited from his father and mother, respectively. To our knowledge, the above mutations have not been described in any database or previous literature. Total parenteral nutrition was employed as mainstay of therapy, and hydrocortisone (1 mg/kg/dose, every 4 hours) was used to maintain blood glucose levels. The patient's final prognosis was poor after discharged from the hospital.

CONCLUSIONS

This case presented with mild platelet abnormality and intractable hypoglycemia, which extends the known mutation and phenotype of THES. The clinical features of Chinese patient are consistent with other ethnicity. Molecular diagnosis is useful for patients with unexplained intractable diarrhea, which puts an end to a long diagnostic odyssey.

Case Report: A Novel Homozygous Frameshift Mutation of the SKIV2L Gene in a Trichohepatoenteric Syndrome Patient Presenting With Short Stature, Premature Ovarian Failure, and Osteoporosis

Background: Trichohepatoenteric syndrome (THES) is a rare Mendelian autosomal recessive genetic disease characterized by intractable diarrhea, woolly hair, facial abnormality, immune dysfunction, and intrauterine growth restriction. THES mutations are found in the TTC37 and SKIV2L genes, which encode two components of the human superkiller (SKI) complex.

Methods and results: We report one case of a 32-year-old woman of Chinese descent with THES, who was born with a low weight (2000 g). She had intractable diarrhea during the neonatal period and was allergic to cow’s milk and condensed milk, but did not require total parenteral nutrition. She experienced menarche at age 12 and amenorrhea at age 28. In May 2019, the patient presented with a left fibular head fracture and was diagnosed with osteoporosis. Genetic testing showed a novel mutation in exon1 [p.E5Afs∗37 (c.12_13del)] of SKIV2L, which is composed of 28 exons. After the diagnosis, hormone replacement therapy was prescribed, in addition to the routine calcium and vitamin D supplements.

Conclusion: This case expands the clinical characteristic and phenotype spectrum of THES, providing further understanding of SKIV2L and its autoimmune influence.

Phenotypic heterogeneity and genotypic spectrum of inborn errors of immunity identified through whole exome sequencing in a Thai patient cohort

BACKGROUND

Inborn errors of immunity (IEI) comprise more than 400 rare diseases with potential life-threatening conditions. Clinical manifestations and genetic defects are heterogeneous and diverse among populations. Here, we aimed to characterize the clinical, immunologic, and genetic features of Thai pediatric patients with IEI. The use of whole-exome sequencing (WES) in diagnosis and clinical decision making was also assessed.

METHODS

Thirty six unrelated patients with clinical and laboratory findings consistent with IEI were recruited from January 2010 to December 2020. WES was performed to identify the underlying genetic defects.

RESULTS

The median age of disease onset was 4 months (range: 1 month to 13 years), and 24 were male (66.7%). Recurrent sinopulmonary tract infection was the most common clinical presentation followed by septicemia and severe pneumonia. Using WES, we successfully identified the underlying genetic defects in 18 patients (50%). Of the 20 variants identified, six have not been previously described (30%). According to the International Union of Immunological Societies (IUIS), 38.9% of these detected cases (7/18) were found to harbor variants associated with genes in combined immunodeficiencies with associated or syndromic features (Class II).

CONCLUSION

The diagnostic yield of WES in this patient cohort was 50%. Six novel genetic variants in IEI genes were identified. The clinical usefulness of WES in IEI was demonstrated, emphasizing it as an effective diagnostic strategy in these genetically heterogeneous disorders.

Singapore Undiagnosed Disease Program: Genomic Analysis aids Diagnosis and Clinical Management

OBJECTIVE

Use next-generation sequencing (NGS) technology to improve our diagnostic yield in patients with suspected genetic disorders in the Asian setting.

DESIGN

A diagnostic study conducted between 2014 and 2019 (and ongoing) under the Singapore Undiagnosed Disease Program. Date of last analysis was 1 July 2019.

SETTING

Inpatient and outpatient genetics service at two large academic centres in Singapore.

PATIENTS

Inclusion criteria: patients suspected of genetic disorders, based on abnormal antenatal ultrasound, multiple congenital anomalies and developmental delay.

EXCLUSION CRITERIA

patients with known genetic disorders, either after clinical assessment or investigations (such as karyotype or chromosomal microarray).

INTERVENTIONS

Use of NGS technology-whole exome sequencing (WES) or whole genome sequencing (WGS).

MAIN OUTCOME MEASURES

(1) Diagnostic yield by sequencing type, (2) diagnostic yield by phenotypical categories, (3) reduction in time to diagnosis and (4) change in clinical outcomes and management.

RESULTS

We demonstrate a 37.8% diagnostic yield for WES (n=172) and a 33.3% yield for WGS (n=24). The yield was higher when sequencing was conducted on trios (40.2%), as well as for certain phenotypes (neuromuscular, 54%, and skeletal dysplasia, 50%). In addition to aiding genetic counselling in 100% of the families, a positive result led to a change in treatment in 27% of patients.

CONCLUSION

Genomic sequencing is an effective method for diagnosing rare disease or previous 'undiagnosed' disease. The clinical utility of WES/WGS is seen in the shortened time to diagnosis and the discovery of novel variants. Additionally, reaching a diagnosis significantly impacts families and leads to alteration in management of these patients.

Trichohepatoenteric syndrome: A rare mutation in SKIV2L gene in the first Balkan reported case

Trichohepatoenteric syndrome or syndromic diarrhea is a rare and severe Mendelian autosomal recessive syndrome characterized by intractable diarrhea, facial and hair abnormalities, liver dysfunction, immunodeficiency and failure to thrive. It has been associated with mutations in TTC37 and SKIV2L genes, which encode proteins of the SKI complex that contributes to the cytosolic degradation of the messenger RNA by the cell's exosome. We report a case of a male infant who suffered from typical symptoms and signs of trichohepatoenteric syndrome without immunodeficiency. The patient's genetic testing showed a very rare mutation in SKIV2L gene's 25 exons (p.Glu1038 fs*7 (c.3112_3140del)). Even though our patient was provided with total parenteral nutrition from birth, the child's death in the third year of age highlights the severity of the disease and the poor prognosis of this particular type of genetic predisposition.

Tricho-Hepato-Enteric Syndrome mutation update: Mutations spectrum of TTC37 and SKIV2L, clinical analysis and future prospects

Tricho-Hepato-Enteric syndrome (THES) is a very rare autosomal recessive syndromic enteropathy caused by mutations of either TTC37 or SKIV2L genes. Very little is known of these two gene products in mammals nor of the pathophysiology of the disease. Since the identification of the genes, we have set up the molecular diagnostic of THES in routine, gathering a large cohort with clinical and molecular data. Here, we report the phenotype and genotype analysis of this cohort together with an extensive literature review of THES cases worldwide, that is, 96 individuals harboring mutations in one gene or the other. We set up locus-specific databases for both genes and reviewed the type of mutation as well as their localization in the proteins. No hot spot is evidenced for any type of mutation. The phenotypic analysis was first made on the whole cohort but is limited due to heterogeneity in clinical descriptions. We then examined the lab diagnostic cohort in detail for clinical manifestations. For the first time, we are able to suggest that patients lacking SKIV2L seem more severely affected than those lacking TTC37, in terms of liver damage and prenatal growth impairment.

The RNA exosome and RNA exosome-linked disease

The RNA exosome is an evolutionarily conserved, ribonuclease complex that is critical for both processing and degradation of a variety of RNAs. Cofactors that associate with the RNA exosome likely dictate substrate specificity for this complex. Recently, mutations in genes encoding both structural subunits of the RNA exosome and its cofactors have been linked to human disease. Mutations in the RNA exosome genes EXOSC3 and EXOSC8 cause pontocerebellar hypoplasia type 1b (PCH1b) and type 1c (PCH1c), respectively, which are similar autosomal-recessive, neurodegenerative diseases. Mutations in the RNA exosome gene EXOSC2 cause a distinct syndrome with various tissue-specific phenotypes including retinitis pigmentosa and mild intellectual disability. Mutations in genes that encode RNA exosome cofactors also cause tissue-specific diseases with complex phenotypes. How mutations in these genes give rise to distinct, tissue-specific diseases is not clear. In this review, we discuss the role of the RNA exosome complex and its cofactors in human disease, consider the amino acid changes that have been implicated in disease, and speculate on the mechanisms by which exosome gene mutations could underlie dysfunction and disease.

Management of syndromic diarrhea/tricho-hepato-enteric syndrome: A review of the literature

Syndromic diarrhea/tricho-hepato-enteric syndrome (SD/THE) is a rare disease linked to the loss of function of either TTC37 or SKIV2L, two components of the SKI complex. It is characterized by a combination of 9 signs (intractable diarrhea, hair abnormalities, facial dysmorphism, immune abnormalities, IUGR/SGA, liver abnormalities, skin abnormalities, congenital heart defect and platelet abnormalities). We present a comprehensive review of the management of SD/THE and tested therapeutic regimens. A review of the literature was conducted in May 2017: 29 articles and 2 abstracts were included describing a total of 80 patients, of which 40 presented with mutations of TTC37, 14 of SKIV2L. Parenteral nutrition was used in the management of 83% of the patients and weaned in 44% (mean duration of 14.97 months). Immunoglobulins were used in 33 patients, but data on efficacy was reported for 6 patients with a diminution of infection (n = 3) or diarrhea reduction (n = 2). Antibiotics (n = 11) provided no efficacy. Steroids (n = 17) and immunosuppressant drugs (n = 13) were used with little efficacy and mostly in patients with IBD-like SD/THE. Hematopoietic stem cell transplantation (HSCT) was performed in 4 patients: 2 died, for one it corrected the immune defects but not the other features and for the last one, it provided only a partial improvement. Finally, no specific diet was effective except for some contradictory reports for elemental formula. In conclusion, the management of SD/THE mainly involves parenteral nutrition and immunoglobulin supplementation. Antibiotics, steroids, immunosuppressants, and HSCT are not recommended as principle treatments since there is no evidence of efficacy.

Novel mutations in SKIV2L and TTC37 genes in Malaysian children with trichohepatoenteric syndrome

Trichohepatoenteric syndrome (THES) is a rare autosomal recessive disorder that is classically associated with intractable diarrhea with an onset within the first few months of life. Herein, we investigated and reported novel mutations in two causal genes in 3 Malaysian cases. Genomic DNA was extracted from peripheral blood obtained from patients in two Malaysian Chinese families. The exons of SKIV2L and TTC37 genes were amplified and sequenced by bi-directional sequencing to identify the point mutations within the coding sequence. Three Chinese boys from two families with characteristic features and clinical course were diagnosed with THES. In family-1, two point mutations were identified in the SKIV2L gene (c.1891G>A and c.3187C>T). In family-2, a single-nucleotide duplication (c.3426dupA) was found in the TTC37 gene. These mutations cause the production of abnormal non-functional gene product leading to the clinical manifestations in the patients. We reported three point mutations, which have not been previously described in other patients with THES in SKIV2L and TTC37 genes, including one nonsense, one frameshift, and one missense mutations.

Identifying Mutations of the Tetratricopeptide Repeat Domain 37 (TTC37) Gene in Infants With Intractable Diarrhea and a Comparison of Asian and Non-Asian Phenotype and Genotype: A Global Case-report Study of a Well-Defined Syndrome With Immunodeficiency

Syndromic diarrhea/tricho-hepato-enteric syndrome (SD/THE) is a rare, autosomal recessive and severe bowel disorder mainly caused by mutations in the tetratricopeptide repeat domain 37 (TTC37) gene which act as heterotetrameric cofactors to enhance aberrant mRNAs decay. The phenotype and immune profiles of SD/THE overlap those of primary immunodeficiency diseases (PIDs). Neonates with intractable diarrhea underwent immunologic assessments including immunoglobulin levels, lymphocyte subsets, lymphocyte proliferation, superoxide production, and IL-10 signaling function. Candidate genes for PIDs predisposing to inflammatory bowel disease were sequencing in this study. Two neonates, born to nonconsanguineous parents, suffered from intractable diarrhea, recurrent infections, and massive hematemesis from esopharyngeal varices due to liver cirrhosis or accompanying Trichorrhexis nodosa that developed with age and thus guided the diagnosis of SD/THE compatible to TTC37 mutations (homozygous DelK1155H, Fs*2; heterozygous Y1169Ter and InsA1143, Fs*3). Their immunologic evaluation showed normal mitogen-stimulated lymphocyte proliferation, superoxide production, and IL-10 signaling, but low IgG levels, undetectable antibody to hepatitis B surface antigen and decreased antigen-stimulated lymphocyte proliferation. A PubMed search for bi-allelic TTC37 mutations and phenotypes were recorded in 14 Asian and 12 non-Asian cases. They had similar presentations of infantile onset refractory diarrhea, facial dysmorphism, hair anomalies, low IgG, low birth weight, and consanguinity. A higher incidence of heart anomalies (8/14 vs 2/12; P = 0.0344, Chi-square), nonsense mutations (19 in 28 alleles), and hot-spot mutations (W936Ter, 2779-2G>A, and Y1169Ter) were found in the Asian compared with the non-Asian patients. Despite immunoglobulin therapy in 20 of the patients, 4 died from liver cirrhosis and 1 died from sepsis. Patients of all ethnicities with SD/THE with the characteristic triad of T nodosa, hepatic cirrhosis, and intractable enteropathy have low IgG, poor vaccine response and/or decreased antigen-stimulated lymphocyte proliferation. This is now better classified into the subgroup of "well-defined syndromes with immunodeficiency" (the update termed as "combined immunodeficiencies with associated or syndromic features") than "predominantly antibody deficiencies" in the update PIDs classification, and requires optimal interventions.