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Aims: This study aimed to investigate associations between renal and extrarenal manifestations of mitochondrial diseases and their natural history as well as predictors of renal disease severity and overall disease outcome. The secondary aim was to generate a protocol of presymptomatic assessment and monitoring of renal function in patients with a defined mitochondrial disease. Methods: A multicenter, retrospective cohort study was performed by the Mitochondrial Clinical and Research Network (MCRN). Patients of any age with renal manifestations associated with a genetically verified mitochondrial disease were included from 8 expert European centers specializing in mitochondrial diseases: Gothenburg, Oulu, Copenhagen, Bergen, Helsinki, Stockholm, Rotterdam, and Barcelona. Results: Of the 36 patients included, two-thirds had mitochondrial DNA-associated disease. Renal manifestations were the first sign of mitochondrial disease in 19%, and renal involvement was first identified by laboratory tests in 57% of patients. Acute kidney injury occurred in 19% of patients and was the first sign of renal disease in the majority of these. The most common renal manifestation was chronic kidney disease (75% with stage 2 or greater), followed by tubulopathy (44.4%), the latter seen mostly among patients with single large-scale mitochondrial DNA deletions. Acute kidney injury and tubulopathy correlated with worse survival outcome. The most common findings on renal imaging were increased echogenicity and renal dysplasia/hypoplasia. Renal histology revealed focal segmental glomerulosclerosis, nephrocalcinosis, and nephronophthisis. Conclusion: Acute kidney injury is a distinct renal phenotype in patients with mitochondrial disease. Our results highlight the importance to recognize renal disease as a sign of an underlying mitochondrial disease. Acute kidney injury and tubulopathy are 2 distinct indicators of poor survival in patients with mitochondrial diseases.

Cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C) deficiency due to the homozygous PCK1 variant has recently been associated with childhood-onset hypoglycemia with a recognizable pattern of abnormal urine organic acids. In this study, 21 children and 3 adult patients with genetically confirmed PEPCK-C deficiency were diagnosed during the years 2016 to 2019 and the available biochemical and clinical data were collected. All patients were ethnic Finns. Most patients (22 out of 24) had a previously published homozygous PCK1 variant c.925G>A. Two patients had a novel compound heterozygous PCK1 variant c.925G>A and c.716C>T. The laboratory results showed abnormal urine organic acid profile with increased tricarboxylic acid cycle intermediates and inadequate ketone body production during hypoglycemia. The hypoglycemic episodes manifested predominantly in the morning. Infections, fasting or poor food intake, heavy exercise, alcohol consumption, and breastfeeding were identified as triggering factors. Five patients presented with neonatal hypoglycemia. Hypoglycemic seizures occurred in half of the patients (12 out of 24). The first hypoglycemic episode often occurred at the age of 1–2 years, but it sometimes presented at a later age, and could re-occur during school age or adulthood. This study adds to the laboratory data on PEPCK-C deficiency, confirming the recognizable urine organic acid pattern and identifying deficient ketogenesis as a novel laboratory finding. The phenotype is expanded suggesting that the risk of hypoglycemia may continue into adulthood if predisposing factors are present.

Background: In Henoch–Schönlein nephritis (HSN), a risk factor for unfavorable outcome is prolonged proteinuria, but the value of renal biopsies in prognosis assessment is debatable. Methods: We evaluated serial renal biopsies from 26 HSN patients. Follow-up biopsy occurred at median 2.1 years after diagnostic biopsy. Patients formed two groups at the follow-up biopsy: patients without proteinuria (group I; n = 11) and with proteinuria (group II; n = 15). Biopsies underwent evaluation according to three classifications: International Study of Kidney Disease in Children (ISKDC), Oxford (MEST-C), and semiquantitative classification (SQC) including an activity and chronicity score. Analysis also included expression of pro-fibrotic (alpha-smooth muscle actin and vimentin) and inflammatory (P-selectin glycoprotein ligand-1) molecules in the diagnostic biopsy specimens. Definition of unfavorable outcome was active renal disease or reduced renal function at last follow-up. Results: Between the biopsies, SQC chronicity score increased in 22 (85%) patients, whereas activity score and ISKDC grade decreased in 21 (81%) and 17 (65%), respectively. Of the MEST-C parameters, endocapillary proliferation (from 83 to 13%; p < 0.001) and crescents (from 63 to 25%; p = 0.022) showed significant reduction, and segmental glomerulosclerosis (from 38 to 79%; p = 0.006) significant increment. These changes occurred similarly in groups I and II. Expression of the pro-fibrotic and inflammatory molecules showed no clinically significant differences between groups I and II. None in group I and five (33%) patients in group II had unfavorable outcome (p = 0.053). Conclusions: Our results suggest that follow-up biopsies provide limited additional information to clinical symptoms in HSN outcome prediction.

Background: Tubulointerstitial nephritis (TIN) and uveitis syndrome (TINU) are likely to be autoimmune diseases. Based on previous studies, adults with isolated idiopathic uveitis have polymorphisms in interleukin 10 (IL-10) and tumor necrosis factor α (TNF-α) genes. We aimed to evaluate the presence of IL-10 and TNF-α polymorphisms in a nationwide cohort of pediatric TIN/TINU patients. Methods: Single nucleotide polymorphisms in IL-10 (+434T/C, +504G/T, -1082G/A, -2849C/T) and in TNFα (-308G/A, -238G/A, -857C/T) genes were genotyped in 30 well-defined pediatric patients with idiopathic TIN/TINU syndrome. Control group frequencies for these SNPs were obtained from 393 independent Finnish subjects. Results: The homozygous minor allele in IL-10 +434T (rs2222202) and IL-10+504G (rs3024490) was found in all patients with TIN or TINU syndrome while the frequency of these minor alleles in the control population was 44% and 23%, respectively (p <0.001). In IL-10 SNP -2849 (rs6703630) a significant difference was found with genotype TT in all patients (p = 0.004) and in subgroups with TINU syndrome (p = 0.017) and TINU syndrome with chronic uveitis (p = 0.01) compared to reference population. There were no statistical differences in any of the studied TNF-α genotypes between TIN/TINU patients and control population. Conclusions: A significant difference in the frequency of IL-10+434T and +504G alleles was found between TIN/TINU patients and control population. Genotype -2849TT was more frequently present in patients with TINU syndrome than in the reference subjects. Genetic variation in the inflammatory mediators may predispose to autoimmune nephritis and uveitis.

Background: Tubulointerstitial nephritis (TIN) is an inflammatory disease of unknown pathogenesis. To evaluate a possible role of regulatory T cells (Tregs) in the pathophysiology of TIN with (TINU) and without uveitis, we investigated the presence and quantity of FOXP3⁺ T regulatory lymphocytes in diagnostic kidney biopsies from pediatric patients. Methods: A total of 33 patients (14 TIN and 19 TINU) were enrolled. The quantity of CD4⁺, FOXP3⁺ and double-positive T cells in formalin-fixed kidney biopsies was determined using double label immunohistochemistry with anti-human CD4 and FOXP3 antibodies. Results: FOXP3 staining was successful in all 33 patients. In patients with chronic uveitis, the density of FOXP3⁺ cells was significantly lower (p = 0.046) than in TIN patients without uveitis or with uveitis lasting <3 months. CD4+ staining was successful in 23 patients. The density of all lymphocytes (CD4⁺, CD4⁺FOXP3⁺ and FOXP3⁺ cells) was significantly lower (p = 0.023) in patients with chronic uveitis than in other patients. Conclusions: FOXP3⁺ T cells are present in kidney biopsy samples from TIN and TINU patients. In patients with chronic uveitis, the density of FOXP3⁺ T cells is significantly lower than in other patients, suggesting a different pathomechanism for these clinical conditions.

The aim of this work was to describe the clinical features and clinical course of Henoch-Schönlein purpura (HSP) in a prospective setting, to compare the efficacy of cyclosporine A (CyA) and methylprednisolone (MP) pulses for the treatment of severe HSP nephritis (HSN) and to study the effect of prophylactic prednisone treatment given at disease onset on the long-term outcome. A total of 223 children with newly diagnosed HSP were followed up prospectively for 6 months. Patients with severe HSN also had extrarenal symptoms more frequently during this time. Protein loss via the intestine was more common than previously described, occurring in 3% of the patients. HSN developed in the early course of the disease. The results suggest that weekly urine dipstick tests are indicated for 2 months after HSP onset and individually for over 6 months in cases of HSN or HSP recurrences. Prednisone did not affect the frequency or timing of the appearance of HSN. The efficacy of CyA and MP treatments was evaluated in a trial with a mean follow-up time of 6 years involving 24 paediatric patients (11 CyA, 13 MP), 15 of whom were randomized and 9 were treated according to the given protocol without randomization. Oral CyA was not inferior to intravenous MP pulses and proved to be an efficient, safe steroid-sparing treatment for severe HSN. All the CyA-treated patients achieved remission of nephrotic-range proteinuria within 3 months, while remission was achieved more slowly in the MP group and only in 6/13 (46%) with the initial treatment. There was no difference in the renal biopsy findings two years after initiation of the therapy. The 8-year outcome of HSP was assessed by means of a health questionnaire in 160 (94%) of the 171 former patients in the randomized placebo-controlled prednisone trial and in 138 (81%) with urine analysis and measurement of blood pressure. HSP carried a good prognosis, although skin relapses occurred up to a decade after the initial onset and cou, Tiivistelmä Väitöskirjan tarkoituksena oli kuvata Henoch-Schönleinin purppuran (HSP) oireita ja taudinkulkua, verrata siklosporiini A:n (CyA) ja metyyliprednisolonipulssihoidon (MP-pulssihoidon) tehoa vaikean HSP-nefriitin (HSN) hoidossa ja selvittää taudin alussa annetun prednisonihoidon vaikutusta pitkäaikaisennusteeseen. Taudinkulkua seurattiin prospektiivisesti 6 kuukauden ajan diagnoosista 223 lapsipotilaan aineistossa. Potilailla, joilla oli vaikea HSN, esiintyi myös muita oireita pitempään. Proteiinin menetystä suolistoon esiintyi 3 %:lla, mikä on aiemmin kuvattua yleisempää. HSN ilmaantui taudin alkuvaiheessa. Tutkimustulosten perusteella viikoittainen virtsanäytteiden seuranta riittää 2 kuukauden ajan taudin alusta. Seuranta-aikaa tulee pidentää yksilöllisesti yli 6 kuukauden, jos potilaalla todetaan HSN tai HSP uusiutuu. Prednisonilla ei todettu olevan vaikutusta HSN:n yleisyyteen tai ilmaantumisaikaan. CyA- ja MP-hoitojen tehoa vaikeaan HSN:n seurattiin 24 lapsipotilaan aineistossa (11 CyA, 13 MP) 6 vuoden ajan. Potilaista 15 satunnaistettiin hoitoryhmiin ja 9 hoidettiin tutkimussuunnitelman mukaan ilman satunnaistamista. Suun kautta otettu CyA vaikutti hoidoista tehokkaammalta, sillä kaikilla potilailla nefroottistasoinen valkuaisvirtsaisuus hävisi kolmessa kuukaudessa. MP-hoitoa saaneista vain 6/13 (46 %) pääsi remissioon MP-hoidolla ja hekin CyA-hoidettuja hitaammin. Kaksi vuotta tutkimuksen alusta otettujen munuaisbiopsioiden histologisissa löydöksissä ei ollut eroa ryhmien välillä. Varhaisen kortisonihoidon pitkäaikaisvaikutuksia arvioitiin 8 vuotta lumekontrolloidun prednisonihoitotutkimuksen jälkeen, jolloin aiemman tutkimuksen 171 potilaasta 160 (94 %) vastasi terveyskyselyyn ja 138 (81 %) osallistui virtsa-analyysin ja verenpaineen mittauksen sisältäneeseen seurantatutkimukseen. HSP:n ennuste oli hyvä, vaikka taudin iho-oireet saattoivat uusia jopa 10 vuoden ajan ja taudin uusiutumisen yhteydessä saattoi ilmaantua myöhäinen HSN. Kohonnut verenpai