Pseudouridylation defect due to DKC1 and NOP10 mutations causes nephrotic syndrome with cataracts, hearing impairment, and enterocolitis.

RNA modifications play a fundamental role in cellular function. Pseudouridylation, the most abundant RNA modification, is catalyzed by the H/ACA small ribonucleoprotein (snoRNP) complex that shares four core proteins, dyskerin (DKC1), NOP10, NHP2, and GAR1. Mutations in DKC1, NOP10, or NHP2 cause dyskeratosis congenita (DC), a disorder characterized by telomere attrition. Here, we report a phenotype comprising nephrotic syndrome, cataracts, sensorineural deafness, enterocolitis, and early lethality in two pedigrees: males with DKC1 p.Glu206Lys and two children with homozygous NOP10 p.Thr16Met. Females with heterozygous DKC1 p.Glu206Lys developed cataracts and sensorineural deafness, but nephrotic syndrome in only one case of skewed X-inactivation. We found telomere attrition in both pedigrees, but no mucocutaneous abnormalities suggestive of DC. Both mutations fall at the dyskerin-NOP10 binding interface in a region distinct from those implicated in DC, impair the dyskerin-NOP10 interaction, and disrupt the catalytic pseudouridylation site. Accordingly, we found reduced pseudouridine levels in the ribosomal RNA (rRNA) of the patients. Zebrafish dkc1 mutants recapitulate the human phenotype and show reduced 18S pseudouridylation, ribosomal dysregulation, and a cell-cycle defect in the absence of telomere attrition. We therefore propose that this human disorder is the consequence of defective snoRNP pseudouridylation and ribosomal dysfunction.

Evolution of viral variants in remdesivir-treated and untreated SARS-CoV-2-infected pediatrics patients.

Detailed information on intrahost viral evolution in SARS-CoV-2 with and without treatment is limited. Sequential viral loads and deep sequencing of SARS-CoV-2 from the upper respiratory tract of nine hospitalized children, three of whom were treated with remdesivir, revealed that remdesivir treatment suppressed viral load in one patient but not in a second infected with an identical strain without any evidence of drug resistance found. Reduced levels of subgenomic RNA during treatment of the second patient, suggest an additional effect of remdesivir on viral replication. Haplotype reconstruction uncovered persistent SARS-CoV-2 variant genotypes in four patients. These likely arose from within-host evolution, although superinfection cannot be excluded in one case. Although our dataset is small, observed sample-to-sample heterogeneity in variant frequencies across four of nine patients suggests the presence of discrete viral populations in the lung with incomplete population sampling in diagnostic swabs. Such compartmentalization could compromise the penetration of remdesivir into the lung, limiting the drugs in vivo efficacy, as has been observed in other lung infections.

Risk factors for catheter-related bloodstream infections associated with home parental nutrition in children with intestinal failure: A prospective cohort study.

BACKGROUND & AIMS: Catheter-related bloodstream infection (CRBSI) is the most common, potentially life-threatening complication of long-term parenteral nutrition (PN). We prospectively assessed the incidence and risk factors for CRBSI in children receiving long-term home PN (HPN) for intestinal failure (IF) in a single IF rehabilitation center. METHODS: Data regarding episodes and potential risk factors for CRBSI in children on HPN were prospectively recorded. RESULTS: Forty-one of 75 children were diagnosed with CRBSI. The overall CRBSI rate was 1.61 per 1000 catheter days. The indications for HPN were gastrointestinal motility disorders in 35%, short bowel syndrome (SBS) in 28% graft versus host disease (GvHD) post bone marrow transplant in 17%, congenital enteropathy in 15%, and severe neurodevelopmental impairment in 5%. Gastrointestinal motility disorders had significantly higher CRBSI rate compared to other groups (p < 0.0005; 2.74 in motility group vs 1.54 in GvHD group vs 0.52 in congenital enteropathies vs 0.36 in SBS group vs 0.67 in severe neurodevelopmental delay). Multivariate analysis revealed that enterocutaneous distal stoma (ileostomy or colostomy) (HR 3.35 [95% CI, 1.63-6.86]; p < 0.001), age <2 years (HR 0.28 [95% CI, 0.15-0.53]; p < 0.0001), male sex (HR 2.28 [95% CI, 1.51-3.43]; p < 0.0001), non-use of taurolidine citrate lock (HR 2.70 [95% CI, 1.72-4.11]; p < 0.0001) and gastrointestinal motility disorder (HR 3.02 [95% CI, 1.81-4.91]; p < 0.001) were independent risk factors for developing CRBSI. CONCLUSIONS: Extra care in managing PN connections and disconnections should be taken in children with an underlying gastrointestinal motility disorder, distal enterocutaneous stoma, male sex and those aged <2 years since they are at a significantly higher risk of CRBSI. Early introduction of taurolidine lock should be considered.

Congenital Diarrhea and Cholestatic Liver Disease: Phenotypic Spectrum Associated with MYO5B Mutations.

Myosin Vb (MYO5B) is a motor protein that facilitates protein trafficking and recycling in polarized cells by RAB11- and RAB8-dependent mechanisms. Biallelic MYO5B mutations are identified in the majority of patients with microvillus inclusion disease (MVID). MVID is an intractable diarrhea of infantile onset with characteristic histopathologic findings that requires life-long parenteral nutrition or intestinal transplantation. A large number of such patients eventually develop cholestatic liver disease. Bi-allelic MYO5B mutations are also identified in a subset of patients with predominant early-onset cholestatic liver disease. We present here the compilation of 114 patients with disease-causing MYO5B genotypes, including 44 novel patients as well as 35 novel MYO5B mutations, and an analysis of MYO5B mutations with regard to functional consequences. Our data support the concept that (1) a complete lack of MYO5B protein or early MYO5B truncation causes predominant intestinal disease (MYO5B-MVID), (2) the expression of full-length mutant MYO5B proteins with residual function causes predominant cholestatic liver disease (MYO5B-PFIC), and (3) the expression of mutant MYO5B proteins without residual function causes both intestinal and hepatic disease (MYO5B-MIXED). Genotype-phenotype data are deposited in the existing open MYO5B database in order to improve disease diagnosis, prognosis, and genetic counseling.

Gastroesophageal Reflux Disease and Foregut Dysmotility in Children with Intestinal Failure.

Gastrointestinal dysmotility is a common problem in a subgroup of children with intestinal failure (IF), including short bowel syndrome (SBS) and pediatric intestinal pseudo-obstruction (PIPO). It contributes significantly to the increased morbidity and decreased quality of life in this patient population. Impaired gastrointestinal (GI) motility in IF arises from either loss of GI function due to the primary disorder (e.g., neuropathic or myopathic disorder in the PIPO syndrome) and/or a critical reduction in gut mass. Abnormalities of the anatomy, enteric hormone secretion and neural supply in IF can result in rapid transit, ineffective antegrade peristalsis, delayed gastric emptying or gastroesophageal reflux. Understanding the underlying pathophysiologic mechanism(s) of the enteric dysmotility in IF helps us to plan an appropriate diagnostic workup and apply individually tailored nutritional and pharmacological management, which might ultimately lead to an overall improvement in the quality of life and increase in enteral tolerance. In this review, we have focused on the pathogenesis of GI dysmotility in children with IF, as well as the management and treatment options.

Diagnosis and management of children with Blue Rubber Bleb Nevus Syndrome: A multi-center case series.

BACKGROUND: Blue Rubber Bleb Nevus Syndrome (BRBNS) is a rare, severe, sporadically occurring disorder characterized by multiple venous malformations. AIMS: To present and analyze a case series of pediatric patients with BRBNS and to describe diagnostic approaches and management options applied. PATIENTS AND METHODS: Multicenter, retrospective study, evaluating the diagnosis and management of children with BRBNS. RESULTS: Eighteen patients diagnosed with BRBNS were included. Cutaneous venous malformations were observed in 78% and gastrointestinal venous malformations in 89%. Lesions were also found in other organs including muscles, joints, central nervous system, eyes, parotid gland, spine, kidneys and lungs. Gastrointestinal lesions were more common in the small intestine than in stomach or colon. The management varied significantly among centers. Endoscopic therapy and surgical therapy alone failed to prevent recurrence of lesions. In younger children and in patients with musculoskeletal or other organ involvement, sirolimus was used with 100% success rate in our series (5 patients treated) although poor compliance with subtherapeutic sirolimus trough levels led to recurrence in a minority. CONCLUSIONS: Considering the multi-organ involvement in BRBNS, diagnosis and management requires a multidisciplinary approach. The treatment includes conservative, medical, endoscopic and surgical options. Prospective multicenter studies are needed to identify the optimal management of this rare condition.