Renal biopsy and family studies in 65 children with isolated hematuria

Extracellular Matrix in Kidney Fibrosis: More Than Just a Scaffold

Kidney fibrosis is the common histological end-point of progressive, chronic kidney diseases (CKDs) regardless of the underlying etiology. The hallmark of renal fibrosis, similar to all other organs, is pathological deposition of extracellular matrix (ECM). Renal ECM is a complex network of collagens, elastin, and several glycoproteins and proteoglycans forming basal membranes and interstitial space. Several ECM functions beyond providing a scaffold and organ stability are being increasingly recognized, for example, in inflammation. ECM composition is determined by the function of each of the histological compartments of the kidney, that is, glomeruli, tubulo-interstitium, and vessels. Renal ECM is a dynamic structure undergoing remodeling, particularly during fibrosis. From a clinical perspective, ECM proteins are directly involved in several rare renal diseases and indirectly in CKD progression during renal fibrosis. ECM proteins could serve as specific non-invasive biomarkers of fibrosis and scaffolds in regenerative medicine. The gold standard and currently only specific means to measure renal fibrosis is renal biopsy, but new diagnostic approaches are appearing. Here, we discuss the localization, function, and remodeling of major renal ECM components in healthy and diseased, fibrotic kidneys and the potential use of ECM in diagnostics of renal fibrosis and in tissue engineering.

Clinical manifestations of IgA nephropathy combined with thin glomerular basement membrane nephropathy in children

Background

Immunoglobulin A nephropathy (IgAN) and thin glomerular basement membrane nephropathy (TBMN) are the most common causes of persistent hematuria during childhood. The objective of this study is to determine the difference in clinical features and laboratory findings between pediatric patients with IgA deposited TBMN and IgAN alone.

Methods

Between January 2000 and March 2009, 95 children were diagnosed with IgAN by renal biopsy. Clinical features and laboratory findings of patients with isolated IgAN and with IgAN plus TBMN were compared; the children diagnosed with IgAN were compared to 127 children who had been diagnosed with TBMN alone during the same period.

Results

There were 71 (74.7%) of a total 95 patients that were diagnosed with isolated IgAN (Group1); in 24 (25.3%) of the 95 patients IgAN was combined with TBMN (Group 2). There was marked difference in the gender distribution between Group 2 and isolated TBMN patients. The degree of proteinuria and pathologic severity was higher in Group 1 compared with Group 2. Gross hematuria was present in both groups. There were no distinguishing features in the other laboratory parameters.

Conclusion

Patients with both IgAN and TBMN seem to have similar clinical features to patients with isolated IgAN; however, the latter tend to have better pathologic and laboratory findings, compared to the patients with IgAN alone.

Familial hematuria

Hematuria is a common presenting complaint in pediatric nephrology clinics and often has a familial basis. This teaching article provides an overview of causes, diagnosis, and management of the major forms of familial hematuria, Alport syndrome, and thin basement membrane nephropathy.

[Alport syndrome or progressive hereditary nephritis with hearing loss]

Alport syndrome is an inherited disorder characterized by progressive hematuric nephritis with structural defects of the glomerular basement membrane, and sensorineural deafness. Ocular abnormalities are frequently associated. The incidence is approximatively 1/5000. The renal disease is severe in male patients and should be responsible for 2% of end-stage renal failure. Alport syndrome is heterogeneous at the clinical and genetic levels. It occurs as a consequence of structural abnormalities in type IV collagen, the major constituent of basement membranes. Six genetically distinct chains of type IV collagen have been identified. Mutations in the COL4A5 gene located at Xq22, and encoding the alpha 5(IV) chain are responsible for X-linked Alport syndrome whereas COL4A3 or COL4A4 located "head to head" on chromosome 2 are involved in the rarer autosomal forms of the disease.

Persistent familial hematuria in children and the locus for thin basement membrane nephropathy

This study examined how often children with persistent familial hematuria were from families where hematuria segregated with the known genetic locus for the condition known as benign familial hematuria or thin basement membrane nephropathy (TBMN) at COL4A3/COL4A4. Twenty-one unrelated children with persistent familial hematuria as well as their families were studied for segregation of hematuria with haplotypes at the COL4A3/COL4A4 locus for benign familial hematuria and at the COL4A5 locus for X-linked Alport syndrome. Eight families (38%) had hematuria that segregated with COL4A3/COL4A4, and four (19%) had hematuria that segregated with COL4A5. At most, eight of the other nine families could be explained by disease at the COL4A3/COL4A4 locus if de novo mutations, non-penetrant hematuria or coincidental hematuria in unaffected family members was present individually or in combination. This study confirms that persistent familial hematuria is not always linked to COL4A3/COL4A4 (or COL4A5) and suggests the possibility of a further genetic locus for benign familial hematuria. This study also highlights the risk of excluding X-linked Alport syndrome on the basis of the absence of a family history or of kidney failure.

Childhood thin GBM disease: review of 22 children with family studies and long-term follow-up

Thin glomerular basement membrane (GBM) disease is generally known to have a good renal prognosis, although renal insufficiency has sometimes been reported and the overlap with Alport syndrome implies that a good prognosis cannot be guaranteed. In order to shed light on long-term prognosis of thin GBM disease we have retrospectively evaluated 22 children with persistent haematuria and biopsy-proven thin GBM. Mean follow up was 7 years (range 2-17 years), mean age at onset was 7 years (range 1.5-15). Biopsies were performed a mean of 3.8 years after detection of hematuria. The light microscopy (LM) and immunofluorescence (IF) findings were essentially unremarkable in all of the children, while electron microscopy (EM) showed thinning of the GBM in all cases and no changes characteristic of Alport syndrome. The family history was positive for renal disease in 17 (77.3%) patients with hematuria in 8 (36.3%) families, and hematuria with renal failure (RF) or deafness in 9 (40.9%). It was completely negative for renal disease in 4 (18.2%) and unavailable in 1 (4.5%). Four patients (18%) showed a decline in renal function after 6, 8, 9 and 12 years of follow-up, and 1 of these also developed hearing impairment. None developed hypertension. Our study suggests that thin GBM disease is not always benign and a child with thin GBM should never be assigned such a prognosis, especially if there is a family history of renal impairment or deafness, where careful follow-up is needed due to the risk of late onset renal failure.

Thin basement membrane nephropathy

Thin basement membrane nephropathy. Thin basement membrane nephropathy (TBMN) is the most common cause of persistent glomerular bleeding in children and adults, and occurs in at least 1% of the population. Most affected individuals have, in addition to the hematuria, minimal proteinuria, normal renal function, a uniformly thinned glomerular basement membrane (GBM) and a family history of hematuria. Their clinical course is usually benign. However, some adults with TBMN have proteinuria >500 mg/day or renal impairment. This is more likely in hospital-based series of biopsied patients than in the uninvestigated, but affected, family members. The cause of renal impairment in TBMN is usually not known, but may be due to secondary focal segmental glomerulosclerosis (FSGS) or immunoglobulin A (IgA) glomerulonephritis, to misdiagnosed IgA disease or X-linked Alport syndrome, or because of coincidental disease. About 40% families with TBMN have hematuria that segregates with the COL4A3/COL4A4 locus, and many COL4A3 and COL4A4 mutations have now been described. These genes are also affected in autosomal-recessive Alport syndrome, and at least some cases of TBMN represent the carrier state for this condition. Families with TBMN in whom hematuria does not segregate with the COL4A3/COL4A4 locus can be explained by de novo mutations, incomplete penetrance of hematuria, coincidental hematuria in family members without COL4A3 or COL4A4 mutations, and by a novel gene locus for TBMN. A renal biopsy is warranted in TBMN only if there are atypical features, or if IgA disease or X-linked Alport syndrome cannot be excluded clinically. In IgA disease, there is usually no family history of hematuria. X-linked Alport syndrome is much less common than TBMN and can often be identified in family members by its typical clinical features (including retinopathy), a lamellated GBM without the collagen alpha3(IV), alpha4(IV), and alpha5(IV) chains, and by gene linkage studies or the demonstration of a COL4A5 mutation. Technical difficulties in the demonstration and interpretation of COL4A3 and COL4A4 mutations mean that mutation detection is not used routinely in the diagnosis of TBMN.

Limited evaluation of microscopic hematuria in pediatrics

OBJECTIVE

The purpose was to determine the value of the standard laboratory and radiologic evaluation of microscopic hematuria in children, and to determine the prevalence of idiopathic hypercalciuria in those children referred for evaluation of unexplained microscopic hematuria.

METHODS

This was a retrospective study of 325 children referred from 1985 to 1994 for the evaluation of asymptomatic microscopic hematuria. The diagnostic studies reviewed included serum creatinine, blood urea nitrogen, serum electrolyte studies, serum complement concentration, antinuclear antibody, urinalysis, urine calcium to creatinine ratios, urinary protein to creatinine ratio and/or 24-hour urinary protein excretion, renal ultrasounds, intravenous pyelograms, voiding cystourethrograms, and historical information.

RESULTS

All creatinine and electrolyte values were normal for age, and none of the biochemical tests obtained in the children with hypercalciuria was abnormal. Of the 325 patients with idiopathic microscopic hematuria, only 18 had abnormal renal ultrasound examinations and 9 voiding cystourethrograms showed low-grade reflux. Hypercalciuria was found in 29 patients. The family history was positive for urolithiasis in 16% of patients without hypercalciuria compared with 14% of patients with hypercalciuria. A positive family history of hematuria was reported in 25% of patients; 62 patients did not have hypercalciuria and 4 of the patients had hypercalciuria. Microscopic hematuria in children is a benign finding in the vast majority of children.

CONCLUSIONS

Our data demonstrate that a renal ultrasound, voiding cystourethrogram, cystoscopy, and renal biopsy are not indicated in the work-up of microscopic hematuria, and microhematuria in the otherwise healthy child is a minimal health threat, rarely indicative of serious illness.

Evaluation of hematuria, proteinuria, and hypertension in adolescents

Signs or symptoms of renal disease in adolescents deserve prompt attention and appropriate evaluation. Adolescents are susceptible to a variety of urinary tract disorders. The key issue in the evaluation of hematuria or proteinuria in adolescents is the existence of concomitant signs of renal disease. For isolated hematuria or proteinuria, demonstration of persistence and a reasoned evaluation are in order. Hypertension in adolescents must be carefully documented and, when present, considered seriously. The fact that most teens with persistent elevated blood pressures have essential hypertension is still a great concern because for most of these adolescents the hypertension will be lifelong and, if left untreated, can be associated with significant morbidity and mortality in the adult years.

Thin GBM nephropathy: premature glomerular obsolescence is associated with hypertension and late onset renal failure

Thin glomerular basement membrane (GBM) nephropathy, also called familial benign hematuria, is characterized by chronic hematuria and uniform thinning of the lamina densa of the glomerular basement membrane. It generally holds an excellent renal prognosis. Alport syndrome in early stages can also show attenuation of the GBM; conversely, renal insufficiency has been reported in familial benign hematuria. To discern early Alport syndrome from thin GBM nephropathy, we carried out a prospective epidemiological study in which 19 normotensive and non-azotemic adult patients with chronic microscopic (18 of 19) and macroscopic (1 of 19) hematuria and biopsy-proven thin GBM nephropathy were followed for a median of 12 years (range 9 to 15 years). Renal biopsies of thin GBM patients at entry showed an increased incidence of focal global glomerulosclerosis when compared to disease controls as IgA nephropathy (P = 0.047) and normal renal tissue (P = 0.0075). All renal biopsies showed the presence of the Goodpasture antigen when tested immunohistochemically. Presence of Alport syndrome was excluded clinically as none of the patients had complaints of hearing loss or abnormalities by audiography and ophthalmology. At the end of follow-up, the incidence of hypertension in thin GBM nephropathy (35%) exceeded that of healthy clinical controls (P = 0.048), and one hypertensive patient developed mild renal failure. In the normotensive patients, the glomerular filtration rate at follow-up as measured by inulin clearance was reduced in three out of seven; these were over 50 years of age. Although no family members were known to have renal disease at inclusion, within four families six elderly first degree relatives had developed unexplained renal insufficiency at the end of follow-up. Thus, thin GBM nephropathy predisposes to premature glomerular obsolescence, leading in time to increased incidences of hypertension and late onset renal insufficiency.

Benign familial hematuria due to mutation of the type IV collagen alpha4 gene

Benign familial hematuria (BFH) is characterized by autosomal dominant inheritance, thinning of the glomerular basement membrane (GBM) and normal renal function. It is frequent in patients with persistent microscopic hematuria, but cannot be clinically differentiated from the initial stages of Alport syndrome, a severe GBM disorder which progresses to renal failure. We present here linkage of benign familial hematuria with the COL4A3 and COL4A4 genes at 2q35-37 (Zmax = 3.58 at theta = 0.0). Subsequently, a glycine to glutamic acid substitution was identified in the collagenous region of the COL4A4 gene. We conclude that type IV collagen defects cause both benign hematuria and Alport syndrome. Furthermore, our data suggest that BFH patients can be carriers of autosomal recessive Alport syndrome.

Hematuria in children

A work-up of a child with suspected hematuria should be undertaken once the primary physician has determined that there actually are red blood cells in the urine and that the hematuria is persistent. Evaluation of a child with persistent microscopic hematuria is facilitated with the determination of whether the blood originates from the glomeruli or whether it comes from elsewhere in the urinary tract. Clues to a glomerular origin include the presence of other manifestations of glomerular disease such as significant proteinuria, RBC casts, and dysmorphic erythrocytes in the urinary sediment, hypertension, and renal insufficiency. Clues to the blood originating from the lower urinary tract include blood clots in the urine, normal erythrocyte morphology, and a pertinent history pointing to the lower tract such as that of trauma, urolithiasis, urological or vascular abnormality, or symptoms of bladder inflammation. The initial evaluation should include a detailed patient history and family history as well as a careful physical examination looking for clues to the presence of a familial, hereditary, or chronic kidney disease. A logical, stepwise initial work-up should follow with the goal of ruling out life-threatening and treatable diseases. If there are no indications for immediate further intervention and the cause of the hematuria remains unclear after the initial work-up has been completed, the parents and patient should be reassured that there are no life-threatening conditions and that although the etiology of the blood in the urine is yet unknown, there is time to follow the patient and plan for additional studies if and when they are indicated. The family's concerns (ie, "Is this cancer?," "Will my child require dialysis and transplantation?") should be addressed frankly, and the physician should mention those diagnoses that may lead to renal failure, but have not been absolutely ruled out yet before a kidney biopsy has been performed, such as Alport's syndrome and IgA nephropathy. The child with isolated microhematuria should be evaluated regularly with urinalyses looking for persistence of the hematuria and appearance of proteinuria, blood pressure measurements, and renal function tests. If the microhematuria persists for 6 to 12 months, a kidney biopsy should be considered.(ABSTRACT TRUNCATED AT 400 WORDS)

Renal biopsy in children with asymptomatic hematuria or proteinuria: survey of pediatric nephrologists

The decision to perform a renal biopsy on children with asymptomatic hematuria or proteinuria remains a problem for clinicians. To assess the current opinion of 349 pediatric nephrologists on this issue, case summaries of a 9-year-old boy with 20 urinary red blood cells per high power field without proteinuria and a 9-year-old boy with 2+ proteinuria (600 mg/day) without hematuria were distributed to each specialist. Seventy-three percent (n = 256; 3:1, male:female) responded. Five percent would biopsy the child with asymptomatic hematuria. The main reasons were academic interest, parental pressure for a diagnosis/prognosis and concern for future economic impact on the child (i.e., life insurance). The determinations to biopsy for hematuria were not related to age or sex of the nephrologist. In contrast, 38% (n = 96) of the pediatric nephrologists would perform a biopsy on the child with proteinuria. The major reasons for biopsy were academic interest and potential for drug therapy. With a normal history, physical examination and laboratory/radiographic evaluation, the vast majority of pediatric nephrologists in North America support a conservative approach to the child with asymptomatic hematuria or proteinuria.

An approach to the evaluation and treatment of microscopic hematuria

Persistent microscopic hematuria in children is most often benign or untreatable. The evaluation of microscopic hematuria in an otherwise healthy child need not require invasive and costly laboratory studies. The initial evaluation must look for signs of life-threatening causes of hematuria, i.e., hypertension, edema, oliguria, or significant proteinuria. If these are absent, a stepwise evaluation is suggested, which includes microscopic examination of the urine for red blood cell casts, a test for proteinuria, serum creatinine, and serial follow-up. Renal biopsy may establish a diagnosis but rarely changes the treatment in a child with asymptomatic isolated microscopic hematuria.