Nephrotic and nephritic syndrome in the newborn

Neonatal nephrotic syndrome: all is not gloomy

Congenital nephrotic syndrome (CNS) is a rare clinical syndrome with a constellation of proteinuria, hypoalbuminaemia and oedema, presenting within 3 months of birth. We present a rare case of neonatal nephrotic syndrome with a probable sepsis induced aetiology. The neonate was referred at day of life 15 with Klebsiella pneumonia sepsis and anasarca. On investigation, the patient had nephrotic range proteinuria, hypoalbuminaemia, generalised anasarca and ascites. The neonate was started on broad-spectrum antibiotics and furosemide. Genetic and other secondary causes of CNS were ruled out. With supportive management and resolution of sepsis, the neonate improved. This case highlights the rare cause of sepsis-induced nephrotic syndrome (NS), which required only supportive treatment without the need for aggressive management of CNS.

Distribution of proteinuria- and albuminuria-to-creatinine ratios in preterm newborns

BACKGROUND

Urine protein assessment is important when glomerular disease or injury is suspected. Normal values of proteinuria already published for preterm newborns suffer from limitation, with small cohorts of patients. This prospective study was conducted to update the urine total protein- and albumin-to-creatinine ratio values.

METHODS

Urine samples were collected from 231 preterm newborns within the first 48 h (D0-1) and/or between 72-120 h of life (D3-4). Total protein, albumin, and creatinine were measured, their distribution and upper-limit values determined.

RESULTS

At D0-1 and D3-4, respectively, the median for the total protein-to-creatinine ratio were 80 and 107 mg/mmol (upper-limit values 223 and 289 mg/mmol) in the whole studied population, 149 and 214 mg/mmol in children born before 29 weeks of gestational age, 108 and 130 mg/mmol in those born between 29 and 33 weeks, and 61 and 93 mg/mmol in those born after 33 weeks. For the albumin-to-creatinine ratio, the median were 12 and 17 mg/mmol (upper-limit values 65 and 62 mg/mmol) in the whole studied population, 22 and 50 mg/mmol in children born before 29 weeks, 21 mg/mmol in those born between 29 and 33 weeks, and 8 and 12 mg/mmol in those born after 33 weeks. The use of nephrotoxic drugs and mechanical ventilation seems to influence proteinuria and albuminuria values.

CONCLUSIONS

We report distribution of proteinuria- and albuminuria-to-creatinine in preterm newborns, including the upper-limit values. These values should be taken into account in the detection and diagnosis of glomerular disease and/or injury in daily clinical practice. Graphical abstract.

Diagnostic and Management Challenges in Congenital Nephrotic Syndrome

Congenital Nephrotic Syndrome (CNS) is defined as nephrotic range proteinuria, hypoalbuminaemia and edema in the first three months of life. CNS is most commonly genetic in cause, with international variance in the incidence of causative mutations. Initially defined by the histopathological appearance, increasingly sophisticated and accessible genetic analyses now provide a body of evidence to suggest that there is a disparity between the histological appearance, the genotype of individuals and the severity of the clinical disease. Through the evolution of management approaches CNS has changed from being an invariably fatal condition to one with appreciable ongoing morbidity and mortality but comparably good outcomes to other causes of paediatric end-stage renal disease, especially following transplantation. This review briefly summarises the more commonly recognised genetic mutations leading to CNS, addresses common management decisions, and concludes with potential therapies for the future.

Detailed clinical manifestations at onset and prognosis of neonatal-onset Denys-Drash syndrome and congenital nephrotic syndrome of the Finnish type

BACKGROUND

Neonatal-onset Denys-Drash syndrome (NODDS) is a distinctive clinical entity and has a poor renal and life outcome. Early diagnosis of NODDS is important for managing disorders of sexual development and determining assigned gender. Although patients with NODDS and congenital nephrotic syndrome of the Finnish type (CNF) present with nephrotic syndrome in neonatal life or infancy, the clinical course of NODDS and factors distinguishing these diseases at onset is unknown.

METHODS

We performed a retrospective cohort study of patients with NODDS and CNF between 1997 and 2017. Patients with nephrotic syndrome and WT1 or NPHS1 mutations with neonatal onset (within 30 days) were eligible.

RESULTS

We studied eight patients with NODDS and 15 with CNF. The median serum creatinine level at onset in the NODDS group was significantly higher (1.85 mg/dL) than that in the CNF group (0.15 mg/dL; P = 0.002). The median placental/fetal weight ratio in the NODDS and CNF group was 41.8% and 21.0%, respectively (P = 0.001). Kaplan-Meier analysis showed that the median number of days for progression to ESRD from onset in the NODDS and CNF groups was 6 and 910 days, respectively (P < 0.001). All patients in the NODDS group were alive at follow-up. Only one patient in the CNF group died of cardiac complications during follow-up.

CONCLUSION

CNS, renal dysfunction at onset, and a relatively large placenta are prominent signs of NODDS. Prognosis for patients with NODDS is satisfactory if appropriate and active management is performed.

Oestrogen inhibits PTPRO to prevent the apoptosis of renal podocytes

Podocytes are a major component of the glomerular filtration membrane, and their apoptosis is involved in a variety of nephrotic syndromes. In the current study, the effects and molecular mechanisms of oestrogen on the proliferation and apoptosis of podocytes were investigated to elucidate the role of oestrogen in the pathogenesis of childhood nephrotic syndrome. The cell proliferation of mouse renal podocytes (MPC-5) and human primary renal podocytes was promoted by 17β-oestradiol (E2) in what appear to be a time-dependent manner. Apoptosis was inhibited by E2 and promoted by the E2 antagonist, tamoxifen. The expression of protein tyrosine phosphatase receptor type O (PTPRO) decreased with the increasing dosage of E2, but increased with the increasing dosage tamoxifen in MPC-5 and human podocytes. The protein, oestrogen receptor (ER)α, was not expressed in MPC-5 and human podocytes. E2 binding to ERβ completely eliminated PTPRO expression in MPC-5. In podocytes, PTPRO was phosphorylated by E2 at the Y1007 and associated with tyrosine-protein kinase JAK2 (JAK2) activation, rather than JAK1 activation. PTPRO was involved in the binding of E2 to signal transducer and activator of transcription (STAT)3 at the Y705 and S727 sites, resulting in the phosphorylation of STAT3 in podocytes. Through PTPRO, E2 also regulated the proliferation and apoptosis of podocytes. In conclusion, oestrogen binding to ERβ, rather than ERα, promoted the proliferation of podocytes and inhibited the apoptosis of podocytes by inhibiting the expression of PTPRO. The mechanism may be associated with the activation of the JAK2/STAT3 signalling pathway. The current study may provide a novel direction for the treatment of childhood nephrotic syndrome.

Hematuria and Proteinuria in Children

PRACTICE GAP

Pediatricians must be aware of screening indications and the evaluation and management of a child with hematuria and/or proteinuria.

OBJECTIVES

After completing this article, readers should be able to: 1. Understand the common causes of proteinuria and hematuria and be able to differentiate between benign and serious causes. 2. Describe screening techniques for initial evaluation of hematuria and proteinuria. 3. Recognize the criteria for diagnosis of proteinuria and hematuria. 4. Plan the appropriate initial evaluation for hematuria and proteinuria and interpret laboratory findings essential for diagnosis. 5. Recognize serious causes of hematuria and proteinuria that warrant immediate referral.

The proximal tubule is the primary target of injury and progression of kidney disease: role of the glomerulotubular junction

There is an alarming global increase in the incidence of end-stage kidney disease, for which early biomarkers and effective treatment options are lacking. Largely based on the histology of the end-stage kidney and on the model of unilateral ureteral obstruction, current investigation is focused on the pathogenesis of renal interstitial fibrosis as a central mechanism in the progression of chronic kidney disease (CKD). It is now recognized that cumulative episodes of acute kidney injury (AKI) can lead to CKD, and, conversely, CKD is a risk factor for AKI. Based on recent and historic studies, this review shifts attention from the glomerulus and interstitium to the proximal tubule as the primary sensor and effector in the progression of CKD as well as AKI. Packed with mitochondria and dependent on oxidative phosphorylation, the proximal tubule is particularly vulnerable to injury (obstructive, ischemic, hypoxic, oxidative, metabolic), resulting in cell death and ultimately in the formation of atubular glomeruli. Animal models of human glomerular and tubular disorders have provided evidence for a broad repertoire of morphological and functional responses of the proximal tubule, revealing processes of degeneration and repair that may lead to new therapeutic strategies. Most promising are studies that encompass the entire life cycle from fetus to senescence, recognizing epigenetic factors. The application of techniques in molecular characterization of tubule segments and the development of human kidney organoids may provide new insights into the mammalian kidney subjected to stress or injury, leading to biomarkers of early CKD and new therapies.

Proteinuria and hematuria in the neonate

PURPOSE OF REVIEW

Neonatal proteinuria and hematuria while not common can have potentially devastating consequences if left undiagnosed and untreated. It is important to distinguish between inherited and acquired causes of proteinuria to initiate appropriate and timely treatment. With regards to hematuria, it is critical to identify true hematuria from pseudo-hematuria to balance between thorough investigation and unnecessary laboratory work up. This review provides an overview of the common causes of hematuria and proteinuria in a neonate.

RECENT FINDINGS

The identification of genetic mutations in nephrotic syndrome has improved our understanding of the role of various proteins that play an important role in maintaining the glomerular filtration barrier. With the advancement in our ability to provide care for extreme premature neonates, the incidence of acute kidney injury has increased in these neonates along with proteinuria and hematuria.

SUMMARY

Persistent proteinuria after neonatal acute kidney injury would be of interest in regards to the risk of developing future chronic kidney disease and hypertension.