Glomerular basement membrane attenuation in familial nephritis and "benign" hematuria

Clinico-pathological correlations in 127 patients in 11 large pedigrees, segregating one of three heterozygous mutations in the COL4A3/ COL4A4 genes associated with familial haematuria and significant late progression to proteinuria and chronic kidney disease from focal segmental glomerulosclerosis

BACKGROUND

Heterozygous mutations in the COL4A3/ COL4A4 genes are currently thought to be responsible for familial benign microscopic haematuria and maintenance of normal long-term kidney function.

METHODS

We report on 11 large Cypriot pedigrees with three such mutations. A total of 236 at-risk family members were genetically studied, and 127 (53.8%) carried a heterozygous mutation. Clinico-pathological correlations were available in all of these patients. Renal biopsies in 21 of these patients all showed various stages of focal, segmental glomerulosclerosis (FSGS). Thirteen of these biopsies were also studied with EM and showed thinning of the glomerular basement membrane.

RESULTS

Mutation G1334E (COL4A3) was found in six pedigrees, mutation G871C (COL4A3) in four and mutation 3854delG (COL4A4) in one pedigree. Clinical and laboratory correlations in all 127 mutation carriers (MC) showed that microscopic haematuria was the only urinary finding in patients under age 30. The prevalence of 'haematuria alone' fell to 66% between 31 and 50 years, to 30% between 51 and 70 and to 23% over age 71. Proteinuria with CRF developed on top of haematuria in 8% of all MC between 31 and 50 years, to 25% between 51 and 70 years and to 50% over 71 years. Altogether 18 of these 127 MC (14%) developed ESRD at a mean age of 60 years. Two members with different mutations married, and two of their children inherited both mutations and developed adolescent, autosomal recessive Alport syndrome (ATS), confirming that these mutations are pathogenic.

CONCLUSIONS

Our data confirm for the first time a definite association of heterozygous COL4A3/COL4A4 mutations with familial microscopic haematuria, thin basement membrane nephropathy and the late development of familial proteinuria, CRF, and ESRD, due to FSGS, indicating that the term 'benign familial haematuria' is a misnomer, at least in this cohort. A strong hypothesis for a causal relationship between these mutations and FSGS is also made. Benign familial haematuria may not be so benign as commonly thought.

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.

COL4A3 mutations and their clinical consequences in thin basement membrane nephropathy (TBMN)

BACKGROUND

Thin basement membrane nephropathy (TBMN) is often caused by mutations in the COL4A3 and COL4A4 genes.

METHODS

We examined 62 unrelated individuals diagnosed with TBMN by renal biopsy (N= 49, 79%) or a positive family history of hematuria but without a biopsy (N= 13, 21%) for mutations in the COL4A3 gene and the COL4A3/COL4A4 promoter. All 52 exons of COL4A3 as well as the COL4A3/COL4A4 promoter were screened with single-stranded conformational polymorphism (SSCP) analysis at 4 degrees C and at room temperature. Amplicons that demonstrated electrophoretic abnormalities were sequenced.

RESULTS

Seven mutations were demonstrated in seven patients: G532C and G584C in exon 25, G596R in exon 26, G695R in exon 28, and IVS 2224 - 11C>T, IVS 2980 + 1G>A and IVS 3518 - 7C>G. No mutations were found in the COL4A3/COL4A4 promoter. Four novel polymorphisms or variants (P116T in exon 6, P690P in exon 27, and G895G and A899A in exon 33) were also demonstrated. In addition, P1109S and Q1495R, which had been described previously but whose status was unclear, were shown to be polymorphisms. All seven mutations described here were associated with hematuria. While one mutation (2980 + 1G>A) was found in an individual who also had proteinuria, none of her family members with the same mutation had increased urinary protein. None of the patients with these seven mutations had renal impairment. Hematuria was completely penetrant in families with the G532C, G584C, G596R, and IVS 2980 + 1G>A mutations but not with the G695R and IVS 3518 - 7C>G mutations.

CONCLUSION

COL4A3 mutations are common in TBMN.

Evaluation of the living kidney donor: current perspectives

Living kidney donation is increasing because of prolonged waiting times on the transplant list, as well as improved outcomes for recipients. In 2001, the number of living donors surpassed the number of deceased donors; this trend likely will continue with ever-increasing margins. Because of this increase, as well as changes in our society's health, it is time to re-review the guidelines for selecting living kidney donors established by Kasiske et al in 1995. A conference will be held this year to review updated literature on medical conditions that impact on renal health. From this, new guidelines for the medical evaluation of living renal donors will be constructed. This review discusses information known to date on the outcomes of individuals undergoing unilateral nephrectomy, the impact of lifestyle on renal function in the setting of nephrectomy, and advancements in the detection of genetically transmitted renal diseases that impact on today's decisions on living donation.

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.

Mutations in theCOL4A4 and COL4A3 genes cause familial benign hematuria

Familial benign hematuria (FBH) is a common autosomal dominant disorder characterized by the presence of persistent or recurrent hematuria. The clinical and pathologic features of this syndrome resemble those of early Alport syndrome (AS), and for this reason a common molecular defect has been proposed. The COL4A3/4 genes seem to be involved in both autosomal AS and FBH. This study involves a linkage analysis for the COL4A3/4 loci and a search for mutations within these genes in 11 biopsy-proven FBH families. Haplotype analysis showed that linkage to the COL4A3/4 locus could not be excluded in eight of nine families. One family was not linked to this locus; however, it included three affected women who could be X-linked AS carriers. Two families were too small to perform linkage analysis. COL4A3 and COL4A4 mutation screening disclosed six new pathogenic mutations, two in the COL4A3 gene (G985V and G1015E) and four in the COL4A4 gene (3222insA, IVS23-1G>C, 31del11, and G960R). It is the first time that mutations within the COL4A3 gene are described in families with FBH. This study clearly demonstrates the main role of the COL4A4 and COL4A3 genes in the pathogenesis of FBH.

Pediatric hematuria and thin basement membrane nephropathy: what is it and what does it mean?

Hematuria is seen frequently in the pediatric population and may signal either benign or serious renal patholosis. A significant proportion of children with asymptomatic hematuria will have thin basement membrane nephropathy (TBMN), a benign disorder, yet there is little information about this entity outside the nephrology literature. This article is designed to provide an information base for pediatric practitioners to assist them in making appropriate decisions regarding diagnosis and care. A review of experience over a decade with 9 children with biopsy-proven TBMN, including follow-up to the present; is presented. In addition, review of literature regarding TBMN, Alport's and Berger's syndromes, which comprise the major clinical entities associated with asymptomatic pediatric hematuria, is presented. Each patient was evaluated for asymptomatic, documented and persistent hematuria. Renal biopsy was performed after clinical evaluation and follow-up. TBMN and Berger's disease (IgA nephropathy) are separable only by renal biopsy results; TBMN is benign and IgA nephropathy may be progressive, mandating referral to a nephrologist. The prognosis of TBMN is excellent.

Asymptomatic hematuria in childhood: a practical approach to evaluation

The differential diagnosis of hematuria with or without proteinuria is extensive, and isolated hematuria is a common problem in children and adolescents. Extensive evaluation is often necessary for the child presenting with macroscopic plus microscopic hematuria including nonglomerular and glomerular etiologies, while children with only isolated microscopic hematuria can generally be followed after baseline evaluation to rule out infection, hypercalciuria, familial hematuria, sickle cell disease, post-streptococcal glomerulonephritis (GN), and structural abnormalities (cysts, stones, obstruction, Wilms tumor). Children with the combination of hematuria and proteinuria require rapid systematic evaluation, generally including renal biopsy, except in cases where post-streptococcal GN can be clearly documented. Post-streptococcal GN occurs 7-21 days after a streptococcal infection, is associated with an acute fall in C3 levels with return to normal by approximately 8 weeks, rarely causes acute renal failure, and in children has a pattern of gradual resolution of hypertension, hematuria, and proteinuria over a course of 6-12 months.

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.

X-linked recessive nephritis with mental retardation, sensorineural hearing loss, and macrocephaly

A family with hereditary nephritis, sensorineural hearing loss, macrocephaly, and mental retardation is reported. X-linked recessive inheritance was suggested by the presence of two affected brothers and a maternal uncle. This association may be a previously unreported variant of Alport's syndrome.

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.

Incidence of thin membrane nephropathy: morphometric investigation of a population sample

To explore the incidence of thin membrane nephropathy (thin basement membrane syndrome, benign familial haematuria), glomerular basement membrane thickness was assessed by light and electron microscopy and by morphometry in a series of newly transplanted allograft kidneys, in lieu of normal kidney specimens. Five of the 76 donors possessed an abnormally thin basement membrane, similar to that observed in thin membrane nephropathy, while in two others the measurements fell in the overlap range between thin and normal. Seven donors therefore had a definite or possible basement membrane lesion. After taking account of an additional series of controls, unrelated to transplantation, it is suggested that the incidence of this abnormality in the general population lies between 5.2% and 9.2%. Circumstances did not allow any association between a thin basement membrane and haematuria or other clinical manifestations to be detected.

Thin basement membrane nephropathy as a cause of recurrent haematuria in childhood

A survey of 69 children presenting with recurrent or persistent haematuria and submitted to percutaneous renal biopsy at this hospital over a 17-year period, was performed to establish the incidence of thin basement membrane nephropathy (TBMN). A diagnosis of primary glomerular disease was established in 44 (IgA nephropathy in 16, Alport's syndrome in 13 and other varieties of glomerulonephritis in 15). Of the remaining 25 patients in whom light microscopical and immunochemical examination revealed no abnormalities, material for electron microscopy was available in 11. In eight of these (five of whom had a family history), TBMN was diagnosed on the basis of ultrastructural morphometric evaluation of glomerular basement membrane thickness. Assuming a similar proportion of the remaining 14 patients with renal biopsy specimens normal by light microscopy had TBMN, the probable frequency of this abnormality in the whole series would be 26%, very similar to that of IgA nephropathy. In the eight TBMN patients the mean glomerular basement membrane thickness ranged between 181 and 236 nm, whilst in 'control' biopsies from children with 'minimal change' nephrotic syndrome or IgA nephropathy, the mean thickness ranged between 242 and 333 nm.

Thin basement membranes in minimally abnormal glomeruli

The light microscopic, immunofluorescence, and electron microscopic appearances of renal biopsy specimens were reviewed and correlated with the clinical and laboratory findings in 61 patients in whom the findings were initially considered to be either normal or to show only minor non-specific abnormalities. In all cases this reassessment included quantitative measurement of glomerular basement membrane thickness by an orthogonal intercept technique. On the basis of the indication for biopsy, patients were classified into three groups: those with haematuria (group I, n = 41); those with a minor degree of proteinuria (group II, n = 16); and those without any urinary abnormality but in whom possible renal disease as a result of systemic disease was suspected (group III, n = 6). About half of the patients with haematuria had significantly thinner glomerular basement membranes than those in the other two groups, irrespective of the variable selected for assessment, and in three this was confirmed in follow up biopsy specimens. Follow up for up to eight years showed that in patients either with or without thin basement membranes haematuria commonly persisted, but the long term outlook in all three groups was otherwise good and no patient developed impaired renal function.

Thin-membrane nephropathy--a common cause of glomerular haematuria

Thin-membrane nephropathy recently has been described as a cause of glomerular haematuria. The prognosis of the condition is unclear but it generally is considered to be benign. In a series of 92 patients with glomerular haematuria, thin-membrane nephropathy was found to be a common cause, occurring in 26 (28%) patients. Sixteen patients were women. The mean age was 42 years. Four patients had a family history of renal disease or haematuria and no patient was deaf. Haematuria had been present from six days to 30 years. Loin pain occurred in 31% of patients. Hypertension was not a feature and mild renal impairment was present in one case only, while a further three cases showed proteinuria at a level of greater than 500 mg of protein per day. Glomerular basement membranes in patients with thin-membrane nephropathy gave a mean (+/- standard deviation) width of 319 + 37 nm which was significantly (P less than 0.002) less than the control value of 394 +/- 61 nm. On the basis of clinical features and serological parameters, thin-membrane nephropathy could not be separated from other renal causes of haematuria but required careful electronmicroscopic examination of renal biopsy material to establish the diagnosis. Limited follow-up has confirmed the good prognosis of the condition.

Electron microscopy in the diagnosis of pediatric disease

Electron microscopy, although not able to solve all diagnostic dilemmas, is an essential adjunct to the analysis of pathologic processes. The importance of correct specimen handling for ultrastructural study is highlighted. Some diseases encountered in pediatrics, in which the ultrastructural findings are well established, are illustrated. New technologies that show promise for wider application to problems in pathology also are considered in this article.

Alterations of glomerular basement membrane relevant to haematuria

To elucidate the morphological basis of glomerular haematuria, morphometric analysis of the glomerular basement membrane (GBM) and lamina densa (LD) was performed on silver impregnated samples for electron microscopy. The cases studied consisted of 3 groups: group A, normal controls, being from donors for kidney transplantation; group B, haematuric; and group C, non-haematuric cases with isolated proteinuria. Qualitative analysis revealed that gap formation, splitting, segmental and diffuse thinning of the GBM occur preferentially in haematuric cases. The morphometry of the GBM and LD yielded increased mean values of the GBM and of LD thickness in groups B and C. The coefficient of variation (CV, SD/mean) for the GBM and LD, however, was the highest in group B among the 3 groups, suggesting the most irregular GBM and LD in group B. In addition, CV was significantly higher in cases with splitting, segmental attenuation and gap of the GBM than cases without. The findings suggest that the irregularity of the GBM rather than its mean thickness is clearly associated with splitting and ultimately with haematuria via the gaps produced.

Thin basement membrane syndrome in adults

Eight (two men, six women) cases of adult thin basement membrane syndrome were studied to clarify the clinicopathological characteristics of the disease. The average age at the time of biopsy was 40 years. All the patients had persistent microscopic haematuria, normal renal function, and normal blood pressure, with the exception of one who was hypotensive. Most of them had persistent or transient proteinuria. Renal symptoms were found in four families, although no relative had Alport's syndrome. Renal biopsy findings observed by light and immunofluorescence microscopy did not indicate any important abnormalities, but extensive diffuse thinning of the glomerular basement membrane, ranging from 153 to 213 nm, was a constant finding by electron microscopy. All the patients retained stable renal function at the time of final follow up, indicating a benign prognosis of the syndrome.

Glomerular basement membrane abnormalities associated with apparently idiopathic hematuria: ultrastructural morphometric analysis

In a recent review of 480 renal biopsies, 41 cases were identified in which glomerular basement membrane (GBM) ultrastructural abnormalities were the major lesion. All of the patients had hematuria. None had evidence of immune-mediated glomerulonephritis. Positive family histories of renal disease were present in the majority of cases, and one case of Alport's syndrome was included. Subjectively, the GBM changes were variable but nearly always included membrane thinning. For objective characterization of this glomerular abnormality, a detailed morphometric study of GBM thickness was undertaken: 12 of these patients (study group) were compared with seven patients (control subjects) with subjectively normal glomeruli who underwent biopsy for reasons other than nonsurgical hematuria but who were also thought to have normal glomerular ultrastructure. The seven control subjects had a mean GBM thickness of 394 nm (SD, 19; range, 356 to 432 nm). Of the 12 study group patients, 11 had mean GBM thicknesses significantly different from control values (nine had mean GBM thinning: range, 235 to 327 nm; two had thickening: means, 440 and 469 nm). In the remaining case (Alport's syndrome) the overall mean was normal, but an abnormal distribution of very thin and very thick GBM regions was seen. Of the four apparently normal hematuric patients, significant mean GBM thinning (326 to 347 nm) was demonstrated in three, with an excess of thin GBM in the fourth case, although the mean thickness was normal. Thus, measurable abnormalities were defined in all of the cases of hematuria examined. The GBM measurements confirmed the subjective impression of membrane abnormality, usually attenuation, as the principal finding in this group of hematuric patients. Furthermore, morphometric analysis may reveal subtle changes of GBM thickness missed by subjective assessment.

Long term prognosis of recurrent haematuria

A long term follow up study of 100 children referred with recurrent haematuria for at least one year to two regional paediatric nephrology units is described. The mean duration of follow up was 8.2 years. An adequate renal biopsy was obtained in 96 and eight cases of Alport's syndrome and 10 of IgA nephropathy were diagnosed (20% and 26% respectively of the biopsies examined by electron microscopy and immunofluorescence). Five patients developed end stage renal failure and six hypertension requiring treatment, with the occurrence of these complications increasing progressively with increasing duration of follow up (1% at five years compared with 12% at 10 years). Adverse prognostic features were persistence of microscopic haematuria, proteinuria at presentation, and appreciable changes on renal biopsy. Eighty four patients had first degree relatives tested for haematuria; 30% of these families had another affected member. With long term follow up recurrent haematuria is associated with considerable morbidity and potential mortality.

Isolated hematuria in children: indications for a renal biopsy

Previous reviews of hematuria in children and adolescents have included patients with proteinuria and other renal functional abnormalities such as hypertension and reduced GFR. We report the clinico-pathological correlations in 76 pediatric patients, aged 3 to 19 years, who underwent a renal biopsy because of isolated hematuria during the 10-year period, 1972 to 1981. All specimens were examined by light and electron microscopy and immunofluorescence techniques. The overall prevalence of abnormal renal histology was 56%. The vast majority (41 of 43) of the abnormal biopsy specimens could be classified into four distinct histological categories: (1) Alport syndrome (N = 9); (2) IgA nephropathy (N = 8); (3) thinning of the glomerular basement membrane (N = 17); (4) vascular C3 staining (N = 7). The children were divided into three clinical subgroups (1) isolated microscopic hematuria ( IMH ), N = 42; (2) IMH plus a family history of hematuria in a first degree relative, N = 15; and (3) IMH plus at least one episode of gross hematuria, N = 19. A significant graded increase in the likelihood of obtaining an abnormal renal biopsy was demonstrated (X2 = 10, P less than 0.007) from groups one to three. Sex, age at onset, or duration of hematuria were not associated with an increased proportion of histopathologic abnormalities. These findings indicate that the yield of a renal biopsy in children with isolated hematuria can be predicted accurately from specific clinical characteristics.