Compound heterozygous variants in OTULIN are associated with fulminant atypical late-onset ORAS

Autoinflammatory diseases are a heterogenous group of disorders defined by fever and systemic inflammation suggesting involvement of genes regulating innate immune responses. Patients with homozygous loss-of-function variants in the OTU-deubiquitinase OTULIN suffer from neonatal-onset OTULIN-related autoinflammatory syndrome (ORAS) characterized by fever, panniculitis, diarrhea, and arthritis. Here, we describe an atypical form of ORAS with distinct clinical manifestation of the disease caused by two new compound heterozygous variants (c.258G>A (p.M86I)/c.500G>C (p.W167S)) in the OTULIN gene in a 7-year-old affected by a life-threatening autoinflammatory episode with sterile abscess formation. On the molecular level, we find binding of OTULIN to linear ubiquitin to be compromised by both variants; however, protein stability and catalytic activity is most affected by OTULIN variant p.W167S. These molecular changes together lead to increased levels of linear ubiquitin linkages in patient-derived cells triggering the disease. Our data indicate that the spectrum of ORAS patients is more diverse than previously thought and, thus, supposedly asymptomatic individuals might also be affected. Based on our results, we propose to subdivide the ORAS into classical and atypical entities.

Outcome of membranoproliferative glomerulonephritis and C3-glomerulopathy in children and adolescents

BACKGROUND

Membranoproliferative glomerulonephritis (MPGN) is a rare cause of glomerulopathy in children. Recently, a new classification based on immunohistological features has been established. Infections and anomalies in complement-regulating genes, leading to alternative complement pathway activation, are suspected to trigger the disease. Nevertheless, little is known about optimal treatment and outcome in children with immune-complex-MPGN (IC-MPGN) and C3-glomerulopathy (C3G).

METHODS

The method used is retrospective analysis of clinical, histological, and genetic characteristics of 14 pediatric patients with MPGN in two medical centers.

RESULTS

Mean age of the patients was 10.6 ± 4.5 years. Patients were grouped into C3G (n = 6) and IC-MPGN (n = 8). One patient showed a likely pathogenic variant in the CFHR5 gene. All 10 patients had risk polymorphisms in complement-regulating genes. Most patients were treated with ACE inhibition, steroids, and mycophenolate mofetil. Three patients with C3G received eculizumab. Median follow-up was 2.3 years. After 1 year of disease, three patients (two C3G, one IC-MPGN) reached complete, five patients partial (three IC-MPGN, two C3G), and five patients no remission (four IC-MPGN, one C3G). One patient progressed to end-stage renal disease (ESRD) 6 years after disease onset.

CONCLUSIONS

IC-MPGN and C3G are rare disorders in children. Most patients have signs of complement activation associated with risk polymorphisms or likely pathogenic variants in complement-regulating genes. Steroids and mycophenolate mofetil seem to be effective and for some patients, eculizumab might be a treatment option. Outcome is heterogeneous and precise differentiation between IC-MPGN and C3G is still pending.

Intermediate Follow-up of Pediatric Patients With Hemolytic Uremic Syndrome During the 2011 Outbreak Caused by E. coli O104:H4

Background.

In 2011 Escherichia coli O104:H4 caused an outbreak with >800 cases of hemolytic uremic syndrome (HUS) in Germany, including 90 children. Data on the intermediate outcome in children after HUS due to E. coli O104:H4 have been lacking.

Methods.

Follow-up data were gathered retrospectively from the medical records of patients who had been included in the German Pediatric HUS Registry during the 2011 outbreak.

Results.

Seventy-two of the 89 (81%) patients were included after a median follow-up of 3.0 (0.9-4.7) years. Hypertension and proteinuria were present in 19% and 28% of these patients, respectively. Of 4 patients with chronic kidney disease (CKD) > stage 2 at short-term follow-up, 1 had a normalized estimated glomerular filtration rate, and 3 (4%) had persistent CKD > stage 2. In 1 of these patients, CKD improved from stage 4 to 3; 1 who had CKD stage 5 at presentation received kidney transplantation; and 1 patient required further hemodialysis during follow-up. One patient (1.4%) still had major neurological symptoms at the latest follow-up. Dialysis during the acute phase (P = .01), dialysis duration (P = .01), and the duration of oligo-/anuria (P = .005) were associated with the development of renal sequelae. Patients treated with eculizumab (n = 11) and/or plasmapheresis (n = 13) during the acute phase of HUS had comparable outcomes.

Conclusions.

The overall outcome of pediatric patients after HUS due to E. coli O104:H4 was equivalent to previous reports on HUS due to other types of Shiga toxin-producing E. coli (STEC). Regular follow-up visits in patients are recommended after STEC-HUS.

Presentation of pediatric Henoch-Schönlein purpura nephritis changes with age and renal histology depends on biopsy timing

BACKGROUND

This study correlates the clinical presentation of Henoch-Schönlein purpura nephritis (HSPN) with findings on initial renal biopsy.

METHODS

Data from 202 pediatric patients enrolled in the HSPN registry of the German Society of Pediatric Nephrology reported by 26 centers between 2008 and 2014 were analyzed. All biopsy reports were re-evaluated for the presence of cellular crescents or chronic pathological lesions (fibrous crescents, glomerular sclerosis, tubular atrophy >5%, and interstitial fibrosis >5%).

RESULTS

Patients with HSPN with cellular glomerular crescents were biopsied earlier after onset of nephritis (median 24 vs 36 days, p = 0.04) than those without, whereas patients with chronic lesions were biopsied later (57 vs 19 days, p < 0.001) and were older (10.3 vs 8.6 years, p = 0.01) than those without. Patients biopsied more than 30 days after the onset of HSPN had significantly more chronic lesions (52 vs 22%, p < 0.001), lower eGFR (88 vs 102 ml/min/1.73m², p = 0.01), but lower proteinuria (2.3 vs 4.5 g/g, p < 0.0001) than patients biopsied earlier. Children above 10 years of age had lower proteinuria (1.98 vs 4.58 g/g, p < 0.001), lower eGFR (86 vs 101 ml/min/1.73m², p = 0.002) and were biopsied significantly later after onset of nephritis (44 vs 22 days, p < 0.001) showing more chronic lesions (45 vs 30%, p = 0.03). Proteinuria and renal function at presentation decreased with age.

CONCLUSIONS

In summary, we find an age-dependent presentation of HSPN with a more insidious onset of non-nephrotic proteinuria, impaired renal function, longer delay to biopsy, and more chronic histopathological lesions in children above the age of 10 years. Thus, HSPN presents more like Immunoglobulin A (IgA) nephritis in older than in younger children.

[EXIT - A Possible Intervention for New- and Earlyborn Babies with Severe Hydrops Fetalis and Hydrothoraces on Both Sides]

The EXIT (ex utero intrapartum treatment) procedure is an established method of respiratory protection, originally used in the delivery of fetuses with congenital obstructive airway diseases (tumors in the throat area, hygromas, so-called congenital high airway obstruction syndrome (CHAOS)). Meanwhile, the procedure is also carried out in large perinatal centers for pronounced diaphragmatic hernia or other special indications (EXIT to ECMO, congenital lung airway malformations (CCAM), pulmonary atresia). We present our experience with adapted EXIT procedures in 5 preterm infants with secondary generalized hydrops fetalis and pronounced bilateral hydrothoraces.

Plasma exchange is effective in a 13-year-old girl with steroid-resistant bilateral optic neuritis

We describe a 13-year-old girl presenting with steroid-resistant bilateral optic neuritis. After plasma exchange (PE), the girl experienced full recovery of her visual acuity. During a 4-year follow-up no relapse occurred. As far as we know, this is the first report of PE treatment in optic neuritis in a child.

Persistent defective membrane trafficking in epithelial cells of patients with familial hemophagocytic lymphohistiocytosis type 5 due to STXBP2/MUNC18-2 mutations

BACKGROUND

Familial hemophagocytic lymphohistiocytosis (FHL) is a rare primary immune disorder defined by mutations in the syntaxin binding protein 2 (STXBP2) alias MUNC18-2. Despite defective immunity and a hyper-inflammatory state, clinical findings such as neurological, gastrointestinal, and bleeding disorders are present in a significant number of patients and suggest an impaired expression and function of STXBP2 in cells other than cytotoxic lymphocytes.

PROCEDURE

We investigated four patients with FHL5 suffering from severe enteropathy and one of whom also had renal tubular dysfunction despite successful hematopoietic stem cell transplantation (HSCT). Gastrointestinal and renal biopsy specimens were analyzed by immunohistochemistry and electron microscopy.

RESULTS

Histopathology revealed an intracytoplasmatic accumulation of PAS-positive granules and an enlarged intracytoplasmatic CD10-positive band along the apical pole of enterocytes. Electron microscopy revealed short microvilli and granules filled with electro lucent material. In addition, we described mildly dilated renal tubules and electron micrographs displayed a higher number of cytoplasmic inclusions, electrodense lysosomal and electrolucent endosomal vesicles.

CONCLUSION

Mutations in STXBP2 do not only affect cytotoxic T lymphocytes but also cause changes in the intestinal and renal epithelium resulting in severe, osmotic diarrhea and renal proximal tubular dysfunction. These defects persist after successful treatment of hemophagocytic lymphohistocytosis by HSCT. Clinical manifestations in FHL5 patients despite successful HSCT may therefore be related to defective membrane trafficking in the gut and kidney.

An outbreak of Shiga toxin-producing Escherichia coli O104:H4 hemolytic uremic syndrome in Germany: presentation and short-term outcome in children

BACKGROUND

In May and June 2011 the largest known outbreak of hemolytic uremic syndrome (HUS) occurred in northern Germany. Because, quite unusually, a large number of adults was affected and the causative Escherichia coli strain, serotype O104:H4, showed an atypical virulence factor pattern, it was speculated that this outbreak was associated with an aggressive course and an unfavorable prognosis also in children.

METHODS

Retrospective analysis of medical records of 90 children and comparison to previous outbreak and sporadic case series.

RESULTS

Median age was unusually high (11.5 years) compared with that in historical series. Only 1 patient (1.1%) died in the acute phase. Most patients (67/90 [74%]) received supportive care only. Renal replacement therapy was required in 64 of 90 (71%) of the children. Neurological complications, mainly seizures and altered mental stage, were present in 23 of 90 (26%) patients. Ten patients received plasmapheresis, 6 eculizumab, and 7 a combination of both. After a median follow-up of 4 months, renal function normalized in 85 of 90 (94%) patients, whereas 3 patients had chronic kidney disease stage 3 or 4, and 1 patient (1.1%) still requires dialysis. Complete neurological recovery occurred in 18 of 23 patients. Mild to moderate and major residual neurological changes were present in 3 patients and 1 patient, respectively, although all patients were still improving.

CONCLUSIONS

E. coli O104:H4 caused the largest HUS outbreak in children reported in detail to date and most patients received supportive treatment only. Initial morbidity, as well as short-term outcome, due to this pathogen, is comparable to previous pediatric series of Shiga toxin-producing E. coli HUS.

Suicidal death of erythrocytes in recurrent hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is characterized by hemolytic anemia with fragmented erythrocytes, thrombocytopenia, and acute renal failure. Lack of complement inactivating factor H predisposes to the development of atypical HUS. Little is known about mechanisms linking complement activation with loss of erythrocyte integrity during HUS. Recent studies disclosed that increased cytosolic Ca2+ activity and cellular ceramide trigger programmed erythrocyte death or eryptosis, characterized by cell shrinkage and phosphatidylserine exposure at the erythrocyte surface. In the present study, we investigated whether eryptosis occurs during the course of HUS. To this end, erythrocytes from healthy volunteers were exposed to plasma from a patient with severe idiopathic recurrent HUS secondary to factor H depletion. Phosphatidylserine exposure (Annexin binding), cell volume (forward scatter), cytosolic Ca2+ activity (Fluo3 fluorescence), and ceramide formation [anti-ceramide antibody and enzymatic (diacylgycerol kinase) analysis] were determined. Exposure of erythrocytes to plasma from the patient, but not to plasma from healthy individuals, triggered Annexin binding. The effect of plasma on erythrocyte Annexin binding was abolished by plasmapheresis or filtration at 30 kDa. It was paralleled by formation of ceramide and increase of cytosolic Ca2+ activity. Enhanced Annexin binding of erythrocytes from healthy individuals was observed after exposure to plasma from three other patients with HUS. The proeryptotic effect of patient plasma was mimicked by exposure to the Ca2+ ionophore ionomycin, and eryptosis was potentiated in the presence of cell membrane-permeable C6-ceramide. Furthermore, in vitro complement activation similarly triggered erythrocyte phosphatidylserine exposure, an effect which was blunted by the addition of factor H. In conclusion, our present observations disclose a novel, pathophysiological, factor-H dependent mechanism leading to injury of erythrocytes during the course of hemolytic uremic syndrome.