Trichohepatoenteric syndrome (THES), also known as phenotypic diarrhea or syndromic diarrhea, is a rare autosomal recessive genetic disorder caused by mutations in SKIC2 (THES-type 2) or SKIC3 (THES-type 1) and is characterized by early onset diarrhea, woolly brittle hair, facial dysmorphic features and liver disease. We report the case of a 24-month-old girl who presented with chronic diarrhea since the neonatal period along with intrauterine growth restriction (IUGR), developmental delay, dysmorphic features, congenital heart defects, liver disease, and recurrent infections. The diagnosis was made through whole-exome sequencing analysis, which detected a homozygous variant (c.4070del, p.Pro1357Leufs*10) in the SKIC3 gene. The patient required parenteral nutrition and was hospitalized for the first 10 months of life and then discharged on PN after showing improvement. She remained stable on PN after discharge despite a few admissions for central line infections. Recent follow-up at the age of 2 years revealed that she was stable on long-term parenteral nutrition and that she had advanced chronic liver disease.

Trichohepatoenteric syndrome (THES) is characterized by neonatal-onset intractable diarrhea. It often requires long-term total parenteral nutrition (TPN). In addition, other characteristic findings of the syndrome include growth retardation, facial dysmorphism, hair abnormalities, various immunological problems and other rare system findings. Two genes and their associated pathogenic variants have been associated with this syndrome: SKIC3 and SKIC2.
In this case series, the clinical findings and molecular analysis results of a total of 8 patients from 5 different families who presented with persistent diarrhea and were diagnosed with THES were shared. Pathogenic variants were detected in the SKIC3 gene in 6 of our patients and in the SKIC2 gene in 2 patients. It was planned to compare the clinical findings of our patients with other patients, together with literature data, and to present yet-undefined phenotypic features that may be related to THES. In our case series, in addition to our patients with a novel variant, patient number 2 had a dual phenotype (THES and Spondyloepimetaphyseal dysplasia, sponastrime type) that has not been reported yet. Delay in gross motor skills, mild cognitive impairment, radioulnar synostosis, osteoporosis, nephropathy and cystic lesions (renal and liver) were observed as unreported phenotypic findings.
We are expanding the clinical and molecular repertoire of the syndrome regarding patients diagnosed with THES. We recommend that the NGS (next-generation sequencing) multigene panel should be used as a diagnostic tool in cases with persistent diarrhea.

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.

UNASSIGNED: Trichohepatoenteric syndrome (THES) is caused by pathogenic mutations in TTC37 and SKIV2L genes and characterized by intractable diarrhea, facial dysmorphism, hair abnormality, immunodeficiency, and skin abnormalities. Lipoid proteinosis is caused by pathogenic mutations in ECM1 gene and characterized by deposition of hyaline-like material in various tissues resulting in heterogenous clinical findings.
UNASSIGNED: Four years after the diagnosis and management of THES, due to new clinical findings, another reason for underlying features of the patient was considered. WES was performed and a homozygous c.507delT (p.Arg171GlyfsTer7) mutation in the ECM1 gene was detected.
UNASSIGNED: This case provides an example of co-existence of multiple genetic defects in a single patient born to consanguineous parents.

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.

Trichohepatoenteric syndrome (THES) is a very rare autosomal recessive genetic disorder, which is characterized by intractable diarrhea during infancy, dysmorphic features, immunodeficiency, and a failure to thrive. There are still significant difficulties for patients and clinicians in terms of the management of THES, even though its molecular basis has been uncovered in the last decade. In this article, we have presented two cases relating to siblings that have been diagnosed with the condition. Concerning one of the patients, we described a novel variation (c.2114 + 5G > A) in the TTC37 gene and a mild clinical course; meanwhile, the other one was clinically diagnosed with THES at 17 years of age, but they had seizures and died suddenly. These cases expand the spectrum of clinical findings in relation to THES.

Trichohepatoenteric syndrome is an autosomal recessive genetic disease with an estimated prevalence of 1:100,000. The mutation of the disease is placed either in SKIV2L or TTC37 genes. The onset of presentation is variable, but symptoms usually start with intractable diarrhea associated with woolly hair abnormality, immune dysfunction, and sometimes hepatic abnormality. This case is of a 10-month-old girl who was born at 37 + 2 weeks due to symmetrical intrauterine growth restriction (IUGR), with a low birth weight (1320 g). It was noticed during her stay in NICU that she had excessive diarrhea on day 8. Gastroenterology suggested starting an extensively-hydrolyzed formula, but no improvement noticed. The multidisciplinary teams decided to order whole-exome sequencing analysis after excluding diarrhea causes. The analysis detected a new variant mutation (c.1297C > T) p. (Arg433Cys). To our knowledge, this is the first time detected in a homozygous state in the SKIV2L gene, as this variant mutation has not been described in any previous literature. Our case was managed mainly by total parenteral nutrition. The patient responded to the treatment appropriately.

Tetratricopeptide repeat protein 37 (TTC37) is a causative gene of trichohepatoenteric syndrome (THES). However, little is known about the pathogenesis of this disease. Here, we characterize the phenotype of a Drosophila model in which ski3, a homolog of TTC37, is disrupted. The mutant flies are pupal lethal, and the pupal lethality is partially rescued by transgenic expression of wild-type ski3 or human TTC37. The mutant larvae show growth retardation, heart arrhythmia, triacylglycerol accumulation, and aberrant metabolism of glycolysis and the TCA cycle. Moreover, mitochondrial membrane potential and respiratory chain complex activities are significantly reduced in the mutants. Our results demonstrate that ski3 deficiency causes mitochondrial dysfunction, which may underlie the pathogenesis of THES.

At the central region of the mammalian major histocompatibility complex (MHC) is a complement gene cluster that codes for constituents of complement C3 convertases (C2, factor B and C4). Complement activation drives the humoral effector functions for immune response. Sandwiched between the genes for serine proteinase factor B and anchor protein C4 are four less known but critically important genes coding for essential functions related to metabolism and surveillance of RNA during the transcriptional and translational processes of gene expression. These four genes are NELF-E (RD), SKIV2L (SKI2W), DXO (DOM3Z) and STK19 (RP1 or G11) and dubbed as NSDK. NELF-E is the subunit E of negative elongation factor responsible for promoter proximal pause of transcription. SKIV2L is the RNA helicase for cytoplasmic exosomes responsible for degradation of de-polyadenylated mRNA and viral RNA. DXO is a powerful enzyme with pyro-phosphohydrolase activity towards 5\' triphosphorylated RNA, decapping and exoribonuclease activities of faulty nuclear RNA molecules. STK19 is a nuclear kinase that phosphorylates RNA-binding proteins during transcription. STK19 is also involved in DNA repair during active transcription and in nuclear signal transduction. The genetic, biochemical and functional properties for NSDK in the MHC largely stay as a secret for many immunologists. Here we briefly review the roles of (a) NELF-E on transcriptional pausing; (b) SKIV2L on turnover of deadenylated or expired RNA 3\'→5\' through the Ski-exosome complex, and modulation of inflammatory response initiated by retinoic acid-inducible gene 1-like receptor (RLR) sensing of viral infections; (c) DXO on quality control of RNA integrity through recognition of 5\' caps and destruction of faulty adducts in 5\'→3\' fashion; and (d) STK19 on nuclear protein phosphorylations. There is compelling evidence that a dysregulation or a deficiency of a NSDK gene would cause a malignant, immunologic or digestive disease.

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