Impact of the Omicron Strain on Febrile Convulsions Requiring Hospitalization in Children: A Single-Center Observational Study.

BACKGROUND: The emergence of the Omicron strain of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at the end of December 2021 has drastically increased the number of infected children in Japan, along with the number of children with febrile convulsions, but its clinical impact is unclear. MATERIALS AND METHODS: We compared the frequency of SARS-CoV-2 infection in children hospitalized with febrile convulsions with the frequency of SARS-CoV-2 infection in children with fever and respiratory symptoms without convulsions. RESULTS: In 2021 and 2022, 49 and 58 children required emergency hospitalization for febrile convulsions (FC group) with status epilepticus or cluster spasms, in which 24 and 38 children underwent a Filmarray® respiratory panel test (FA test), respectively, and others received a quantitative antigen test for SARS-CoV-2. In 2022, only six patients tested positive for SARS-CoV-2 (10.3%, 6/58). As a reference group, 655 children aged <10 years who underwent the FA test for fever and respiratory symptoms during the same period were investigated, and 4 (1.8%, 4/223) and 42 (9.7%, 42/432) tested positive for SARS-CoV-2 in 2021 and 2022, respectively. Rhinovirus/enterovirus (RV/EV) was the most frequently detected virus (40.3%, 264/655), followed by respiratory syncytial virus (RSV) (18.9%, 124/655) and parainfluenza virus 3 (PIV3) (7.8%, 51/655). There was no significant difference in the trend of detected viruses between the two groups. CONCLUSIONS: The frequency and severity of febrile convulsions requiring hospitalization associated with SARS-CoV-2 infection of the Omicron strain may be similar to that of other respiratory viruses in children.

Outcome of immunosuppression in children with IgA vasculitis-related nephritis.

BACKGROUND AND HYPOTHESIS: IgA vasculitis with nephritis (IgAVN) is the most common vasculitis in children. Treatment recommendations are, due to a lack of evidence, based on expert opinion resulting in variation. The aim of this study was to describe clinical presentation, treatment and outcome of an extremely large cohort of children with biopsy proven IgAVN to identify prognostic risk factors and signals of treatment efficacy. METHODS: Retrospective data were collected on 1148 children with biopsy proven IgAVN between 2005 and 2019 from 41 international paediatric nephrology centres across 25 countries and analyzed using multivariate analysis. The primary outcome was estimated glomerular filtration rate (eGFR) and persistent proteinuria at last follow up. RESULTS: The median follow up was 3.7 years (IQR 2-6.2). At last follow up, 29% of patients had an eGFR < 90 ml/min/1.73m2, 36% had proteinuria and 3% had chronic kidney disease stage 4-5. Older age, lower eGFR at onset, hypertension and histological features of tubular atrophy and segmental sclerosis were predictors of poor outcome. There was no evidence to support any specific second line immunosuppressive regimen to be superior to others, even when further analysing subgroups of children with reduced kidney function, nephrotic syndrome or hypoalbuminemia at onset. Delayed start of immunosuppressive treatment was associated with a lower eGFR at last follow up. CONCLUSION: In this large retrospective cohort, key features associated with disease outcome are highlighted. Importantly there was no evidence to support that any specific immunosuppressive treatments were superior to others. Further discovery science and well-conducted clinical trials are needed to define accurate treatment and improve outcomes of IgAVN.

Phenotypic Variation in 46,XX Disorders of Sex Development due to the Fourth Zinc Finger Domain Variant of WT1: A Familial Case Report.

INTRODUCTION: The variants in the zinc finger (ZF) domains 1-3 in WT1 are one of the major causes of 46,XY disorders of sex development (DSD). Recently, variants in the fourth ZF (ZF4 variants) were reported to cause 46,XX DSD. However, all the 9 patients reported were de novo, and no familial cases were identified. CASE PRESENTATION AND RESULTS: The proband (16-year-old social female) had a 46,XX karyotype with dysplastic testes and moderate virilization in genitalia. A ZF4 variant, p.Arg495Gln, in WT1 was identified in the proband, her brother, and mother. The mother did not show any virilization with normal fertility, and the 46,XY brother developed normal puberty. CONCLUSION: The phenotypic variations due to the ZF4 variant are extremely broad in 46,XX cases.

Atrophic autoimmune thyroiditis complicated with systemic lupus erythematosus.

Atrophic autoimmune thyroiditis (AAT) is a type of autoimmune thyroiditis that causes hypothyroidism without thyroid enlargement. AAT is distinguished from Hashimoto's disease (HD) by the absence of thyroid enlargement. AAT is rare in children and clinically characterised by severe primary hypothyroidism. Autoimmune thyroiditis, especially HD, is commonly complicated with systemic lupus erythematosus (SLE). Here, we reported the patient with AAT as the initial presentation of SLE complicated with generalised myxoedema, whose presentation was a diagnostic challenge. This patient illustrates the importance of the early recognition of an atypical presentation of SLE patients with autoimmune thyroiditis. It is possible that similar cases have existed in the past but have been overlooked as HD. A large-scale study is necessary to clarify the reality of AAT in SLE.

A novel SLC5A2 heterozygous variant in a family with familial renal glucosuria.

Familial renal glucosuria (FRG) is characterized by persistent glucosuria despite normal blood glucose levels in the absence of overt tubular dysfunction. SGLT2 is a sodium-glucose cotransporter expressed in the proximal tubule; loss-of-function variants in SLC5A2 are the primary cause of FRG. Heterozygous variants have rarely been reported in Japanese individuals. Here, we identified a novel SLC5A2 heterozygous variant, c.1348G>T: p.Gly450Trp, in a Japanese family comprising two children and their father.

Podocytes are lost from glomeruli before completing apoptosis.

Although apoptosis of podocytes has been widely reported in in vitro studies, it has been less frequently and less definitively documented in in vivo situations. To investigate this discrepancy, we analyzed the dying process of podocytes in vitro and in vivo using LMB2, a human (h)CD25-directed immunotoxin. LMB2 induced cell death within 2 days in 56.8 ± 13.6% of cultured podocytes expressing hCD25 in a caspase-3, Bak1, and Bax-dependent manner. LMB2 induced typical apoptotic features, including TUNEL staining and fragmented nuclei without lactate dehydrogenase leakage. In vivo, LMB2 effectively eliminated hCD25-expressing podocytes in NEP25 mice. Podocytes injured by LMB2 were occasionally stained for cleaved caspase-3 and cleaved lamin A but never for TUNEL. Urinary sediment contained TUNEL-positive podocytes. To examine the effect of glomerular filtration, we performed unilateral ureteral obstruction in NEP25 mice treated with LMB2 1 day before euthanasia. In the obstructed kidney, glomeruli contained significantly more cleaved lamin A-positive podocytes than those in the contralateral kidney (50.1 ± 5.4% vs. 29.3 ± 4.1%, P < 0.001). To further examine the dying process without glomerular filtration, we treated kidney organoids generated from nephron progenitor cells of NEP25 mice with LMB2. Podocytes showed TUNEL staining and nuclear fragmentation. These results indicate that on activation of apoptotic caspases, podocytes are detached and lost in the urine before nuclear fragmentation and that the physical force of glomerular filtration facilitates detachment. This phenomenon may be the reason why definitive apoptosis is not observed in podocytes in vivo.NEW & NOTEWORTHY This report clarifies why morphologically definitive apoptosis is not observed in podocytes in vivo. When caspase-3 is activated in podocytes, these cells are immediately detached from the glomerulus and lost in the urine before DNA fragmentation occurs. Detachment is facilitated by glomerular filtration. This phenomenon explains why podocytes in vivo rarely show TUNEL staining and never apoptotic bodies.

Infliximab treatment for refractory COVID-19-associated multisystem inflammatory syndrome in a Japanese child.

Patients with multisystem inflammatory syndrome in children (MIS-C) can develop clinical features resembling Kawasaki disease (KD). A full picture of MIS-C in East Asia which has higher incidence of KD than other regions remains unclear. We report on a 15-year-old Japanese boy with refractory MIS-C who was successfully treated with infliximab. A Japanese boy who was diagnosed with coronavirus disease 2019 (COVID-19) before a month developed MIS-C with fulfilling six principal symptoms of KD. Laboratory data showed extreme hyperferritinemia (11,404 ng/mL), besides lymphopenia and thrombocytopenia. The patient was refractory to initial therapy with intravenous immunoglobulin (IVIG; 2 g/kg), aspirin, and prednisolone. He was therefore administered a second IVIG (2 g/kg) and infliximab (5 mg/kg) on days 7 and 8 from the onset of fever, respectively, which resulted in an improvement of clinical symptoms. Only four Japanese cases with MIS-C were reported and all of them were responsive to IVIG. The hyperferritinemia in this case was distinctive from previously reported MIS-C cases in Japan and other cohorts and may be associated with refractoriness to IVIG therapy. Marked elevation of circulating ferritin levels is known to be induced by tumor necrosis factor-α, which plays a key role in the pathogenesis of both KD and MIS-C. Thus, for MIS-C patients with hyperferritinemia, early intervention with adjunctive infliximab may induce a more rapid resolution of inflammation and improve outcome. Because MIS-C may be heterogeneous with respect to immunopathology, genetic background, clinical phenotypes and response to therapies, optimized treatment strategies according to immunopathogenesis are required.

Association between Immunoglobulin M and Steroid Resistance in Children with Nephrotic Syndrome: A Retrospective Multicenter Study in Japan.

Background: The prognosis of steroid-resistant nephrotic syndrome (SRNS) in children is poorer than steroid-sensitive cases. Diagnosis of SRNS is made after observing the response to the initial 4-week corticosteroid therapy, which might be accompanied by side effects. However, predictive indicators at initial diagnosis remain unknown. We aimed to investigate whether selectivity index (SI) and other indicators at initial diagnosis-for example, serum IgM and total serum protein-albumin ratio (TA ratio, total serum protein level over albumin level)-can predict SRNS. Methods: A total of 80 children were enrolled from seven hospitals in Japan between January 2008 and December 2019 (mean age, 4.7 years; 65% male). Of the children enrolled, 13 (16%, M/F=5:8) had been diagnosed as steroid resistant after initial treatment with steroids. The association between serum IgM (tertile categories: low, 24-133; middle, 134-169; and high, 169.1-510 mg/dl), SI (<0.2 or ≥0.2), and TA ratio (tertile categories: low, 1.8-2.6; middle, 2.62-3.75; and high, 3.8-15.3) at initial diagnosis and steroid resistance was evaluated with logistic regression, adjusting for age and sex. Results: Low levels of serum IgM were significantly associated with steroid resistance (adjusted odds ratio, 6.94; 95% CI, 1.12 to 43.11). TA ratio and SI were not significantly associated with steroid resistance. Conclusions: Low levels of serum IgM at initial diagnosis might predict steroid resistance among Japanese children with idiopathic nephrotic syndrome.

A cellular model of albumin endocytosis uncovers a link between membrane and nuclear proteins.

Cubilin (CUBN) and amnionless (AMN), expressed in kidney and intestine, form a multiligand receptor complex called CUBAM that plays a crucial role in albumin absorption. To date, the mechanism of albumin endocytosis mediated by CUBAM remains to be elucidated. Here, we describe a quantitative assay to evaluate albumin uptake by CUBAM using cells expressing full-length CUBN and elucidate the crucial roles of the C-terminal part of CUBN and the endocytosis signal motifs of AMN in albumin endocytosis. We also demonstrate that nuclear valosin-containing protein-like 2 (NVL2), an interacting protein of AMN, is involved in this process. Although NVL2 was mainly localized in the nucleolus in cells without AMN expression, it was translocated to the extranuclear compartment when coexpressed with AMN. NVL2 knockdown significantly impaired internalization of the CUBN-albumin complex in cultured cells, demonstrating an involvement of NVL2 in endocytic regulation. These findings uncover a link between membrane and nucleolar proteins that is involved in endocytic processes.

A review of clinical characteristics and genetic backgrounds in Alport syndrome.

Alport syndrome (AS) is a progressive hereditary renal disease that is characterized by sensorineural hearing loss and ocular abnormalities. It is divided into three modes of inheritance, namely, X-linked Alport syndrome (XLAS), autosomal recessive AS (ARAS), and autosomal dominant AS (ADAS). XLAS is caused by pathogenic variants in COL4A5, while ADAS and ARAS are caused by those in COL4A3/COL4A4. Diagnosis is conventionally made pathologically, but recent advances in comprehensive genetic analysis have enabled genetic testing to be performed for the diagnosis of AS as first-line diagnosis. Because of these advances, substantial information about the genetics of AS has been obtained and the genetic background of this disease has been revealed, including genotype-phenotype correlations and mechanisms of onset in some male XLAS cases that lead to milder phenotypes of late-onset end-stage renal disease (ESRD). There is currently no radical therapy for AS and treatment is only performed to delay progression to ESRD using nephron-protective drugs. Angiotensin-converting enzyme inhibitors can remarkably delay the development of ESRD. Recently, some new drugs for this disease have entered clinical trials or been developed in laboratories. In this article, we review the diagnostic strategy, genotype-phenotype correlation, mechanisms of onset of milder phenotypes, and treatment of AS, among others.

Amnionless-mediated glycosylation is crucial for cell surface targeting of cubilin in renal and intestinal cells.

Mutations in either cubilin (CUBN) or amnionless (AMN) genes cause Imerslund-Gräsbeck syndrome (IGS), a hereditary disease characterised by anaemia attributed to selective intestinal malabsorption of cobalamin and low-molecular weight proteinuria. Although cubilin protein does not have a transmembrane segment, it functions as a multi-ligand receptor by binding to the transmembrane protein, amnionless. We established a system to quantitatively analyse membrane targeting of the protein complex in cultured renal and intestinal cells and analysed the pathogenic mechanisms of mutations found in IGS patients. A novel CUBN mutation, several previously reported CUBN missense mutations and all previously reported AMN missense mutations resulted in endoplasmic reticulum (ER) retention and completely inhibited amnionless-dependent plasma membrane expression of cubilin. The ER retention of cubilin and amnionless was confirmed in renal proximal tubular cells of a patient with IGS. Notably, the interaction between cubilin and amnionless was not sufficient, but amnionless-mediated glycosylation of cubilin was necessary for their surface expression. Quantitative mass spectrometry and mutagenesis demonstrated that N-linked glycosylation of at least 4 residues of cubilin protein was required for its surface targeting. These results delineated the molecular mechanisms of membrane trafficking of cubilin in renal and intestinal cells.

Altered expression of Crb2 in podocytes expands a variation of CRB2 mutations in steroid-resistant nephrotic syndrome.

BACKGROUND: Steroid-resistant nephrotic syndrome (SRNS) is a genetically heterogeneous disorder for which more than 25 single-gene hereditary causes have been identified. METHODS: Whole exome sequencing was performed in a 3-year-old girl with SRNS. We analyzed the expression of Crb2 and slit diaphragm molecules in the patient's glomeruli, and compared it with that of controls or other nephrotic patients. RESULTS: Whole-exome analysis identified novel compound heterozygous mutations in exons 10 and 12 of CRB2 (p.Trp1086ArgfsX64 and p.Asn1184Thr, each from different parents; Asn1184 within extracellular 15th EGF repeat domain). Renal pathology showed focal segmental glomerulosclerosis with effaced podocyte foot processes in a small area, with significantly decreased Crb2 expression. Molecules critical for slit diaphragm were well-expressed in this patient's podocytes. Crb2 expression was not altered in the other patients with congenital nephrotic syndrome with NPHS1 mutations. CONCLUSIONS: These findings demonstrate that Crb2 abnormalities caused by these mutations are the mechanism of steroid-resistant NS. Although CRB2 mutations previously found in SRNS patients have been clustered within the extracellular tenth EGF-like domain of this protein, the present results expand the variation of CRB2 mutations that cause SRNS.

Effect of eculizumab and recombinant human soluble thrombomodulin combination therapy in a 7-year-old girl with atypical hemolytic uremic syndrome due to anti-factor H autoantibodies.

Atypical hemolytic uremic syndrome (aHUS), which is defined as non-Shiga toxin-associated hemolytic uremic syndrome, is a type of thrombotic microangiopathy. This syndrome presents with hemolytic anemia, thrombocytopenia, and acute kidney injury. Excessive complement activation due to genetic disorders of the complement system or production of autoantibodies to factor H (FH) causes the disease. We report a successful treatment course using eculizumab and recombinant human soluble thrombomodulin (rTMD) for a 7-year-old girl with aHUS due to anti-FH autoantibodies. Although her chief complaints were abdominal pain and loose stools, we were finally able to diagnose her with aHUS because Shiga toxin-producing Escherichia coli was not detected in her feces and a hemolytic assay analyzing FH function was positive. We administrated rTMD to our patient because of signs of disseminated intravascular coagulation. Soon after the therapeutic intervention, the platelet count began to increase and abdominal pain was moderately improved. Plasma exchange limited the efficacy of her disease. Therefore, we administered eculizumab, monoclonal humanized antibody against C5, 3 weeks after admission. Platelet counts immediately increased and kidney function gradually recovered. Genetic disorders were not detected. However, anti-FH autoantibody was observed. There were no symptoms for recurrence of aHUS or kidney dysfunction for 15 months, as a result of the administration of eculizumab every other week. In conclusion, combination therapy of eculizumab and rTMD was effective for an aHUS patient. This therapy may be helpful for improving the prognosis and long-term kidney function of aHUS patients.

Survey of rituximab treatment for childhood-onset refractory nephrotic syndrome.

BACKGROUND: Rituximab (RTX) is a promising option for treating childhood-onset steroid-dependent (SDNS), frequently relapsing (FRNS), and steroid-resistant (SRNS) nephrotic syndrome. METHODS: We retrospectively surveyed RTX treatment for these conditions to evaluate its indications, efficacy and adverse events. Questionnaires were sent to 141 hospitals in Japan. RESULTS: Seventy-four patients (52 SDNS; 3 FRNS; 19 SRNS) were treated with RTX because of resistance to various immunosuppressive agents. Most patients received a single administration of RTX (85%). Forty-one of 53 SDNS/FRNS (77%) and 5 of 17 SRNS (29%) patients successfully discontinued prednisolone (16 SDNS/FRNS and 6 SRNS achieved their first discontinuation since onset), and 17 out of 53 SDNS/FRNS patients (31%) discontinued cyclosporine. However, 28 of the 53 patients (51%) relapsed. Although immunosuppressive agents did not extend B cell depletion, relapses were significantly less if immunosuppressive agents were continued after RTX (P = 0.006; hazard ratio = 0.2). Among the SRNS patients, complete (n = 6) and partial remission (n = 6) were achieved. No life-threatening adverse events were experienced. CONCLUSIONS: Although this was a multi-center survey where treatment of nephrotic syndrome varied between centers, the steroid-sparing effect of RTX in SDNS/FRNS was excellent. If single administration of RTX is chosen, continuation of immunosuppressive agents is recommended for prevention of relapse.

Thrombotic microangiopathy due to multiple autoantibodies related to antiphospholipid syndrome.

BACKGROUND: Antiphospholipid syndrome (APS) is a rare disorder in children. More than half of childhood APS occurs as secondary APS complicated by systemic lupus erythematosus (SLE) and other autoimmune diseases. CASE-DIAGNOSIS/TREATMENT: We encountered a boy with SLE who presented with thrombotic microangiopathy (TMA) due to APS. He was initially diagnosed with SLE and treated with methylprednisolone pulse therapy. However, his renal function rapidly deteriorated. Since poikilocytes were detected, we suspected that his condition was complicated by TMA or APS. Urgent plasma exchange, continuous hemodialysis, and intravenous cyclophosphamide saved the patient and his renal failure ameliorated. A renal biopsy performed at the onset of disease showed multiple microvascular thrombi, diffuse mesangiolysis, and cortical necrosis compatible with TMA. He was positive for anticardiolipin antibody, anti-ß2-glycoprotein I antibody, and lupus anticoagulant as well as anti-phosphatidylserine-prothrombin complex IgG antibody (aPS/PT). Anti-a disintegrin-like and metalloproteinase with thrombospondin type 1 motifs 13 (ADAMTS13) antibody was negative and ADAMTS13 activity was normal. The aPS/PT is thrombogenic and is a newly discovered lupus anticoagulant. CONCLUSIONS: Childhood TMA due to APS has rarely been reported. To the best of our knowledge this is the first report of pediatric TMA due to APS with positive aPS/PT. Physicians need to be aware of aPS/PT in pediatric APS and/or SLE.