The thin glomerular basement membrane in children with haematuria

Identification of COL4A4 variants in Chinese patients with familial hematuria

Background: Benign familial hematuria and Alport syndrome are common causes of familial hematuria among children and young adults, which are attributable to variants in the collagen type IV alpha chain genes, COL4A3, COL4A4, or COL4A5. The study was conducted to identify the underlying genetic causes in patients with familial hematuria. Methods: Two unrelated Han-Chinese pedigrees with familial hematuria were recruited for this study. Whole exome sequencing was combined with in silico analysis to identify potential genetic variants, followed by variant confirmation by Sanger sequencing. Reverse transcription, PCR, and Sanger sequencing were performed to evaluate the effect of the detected splicing variant on mRNA splicing. Results: A novel heterozygous splicing c.595-1G>A variant and a known heterozygous c.1715G>C variant in the collagen type IV alpha 4 chain gene (COL4A4) were identified and confirmed in patients of pedigree 1 and pedigree 2, respectively. Complementary DNA analysis indicated this splicing variant could abolish the canonical splice acceptor site and cause a single nucleotide deletion of exon 10, which was predicted to produce a truncated protein. Conclusions: The two COL4A4 variants, c.595-1G>A variant and c.1715G>C (p.Gly572Ala) variant, were identified as the genetic etiologies of two families with familial hematuria, respectively. Our study broadened the variant spectrum of the COL4A4 gene and explained the possible pathogenesis, which will benefit clinical management and genetic counseling.

Clinical outcomes in pediatric patients with normal renal histopathology

Background

There have been some cases where abnormal histopathologic findings could not be found in the kidney could even with proper specimen collection through percutaneous renal biopsy (PRB) in accordance with its indication. We analyzed the incidence and clinical outcomes of children who showed normal histopathological findings in their PRBs.

Methods

The medical records of 552 pediatric subjects who underwent PRB between 2005 and 2016 were reviewed. Twenty-six subjects were excluded because allograft biopsy was performed in nine subjects, and the age at biopsy was greater than 18 years in 17 subjects. Finally, 526 subjects were enrolled in this study.

Results

Of the 526 pediatric patients, 32 (6.1%) showed no histopathological abnormalities in their PRBs. The male-to-female ratio of the patients was 1.9:1, and the mean ages at the first visit and at biopsy were 10.6 ± 4.1 and 11.4 ± 3.8 years, respectively. In accordance with the biopsy indications, recurrent gross hematuria showed the highest incidence rate, but combined hematuria and proteinuria had the lowest incidence rate regarding normal renal histopathology among all the subjects. At a mean follow-up of 35.5 ± 23.6 months, urinary abnormalities had improved in more than 50% of the subjects with normal renal histopathology, and none of the patients showed progression to end-stage renal disease or required rebiopsy due to symptom worsening during the follow-up period.

Conclusion

The clinical outcomes of children with normal PRB histopathologic findings are generally good. Further studies to evaluate their long-term outcomes are needed.

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.

The Transition from Thin Basement Membranes to Typical Alport Syndrome Morphology in Children

Some children with thin basement membranes (TBM) turn out to have Alport syndrome (AS). In our population of 58 children initially diagnosed with TBM, three were eventually diagnosed with AS. As a group, these three were first biopsied at a younger age, and had gross rather than microscopic hematuria. Only one had lamellations initially. Seven others had some degree of basement membrane lamellations at initial biopsy, but none of these have developed other features of AS. We concluded that at least 5% of children initially demonstrating TBM go on to manifest the classical electron-microscopic findings of AS during childhood. Episodes of gross hematuria with TBM can be a significant clue of AS. Genetic and/or immunofluorescent studies for type IV collagen, and continued long-term follow-up should be done in all children with TBM.

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.

Thin basement membrane nephropathy associated with minimal change disease in a 15-year-old boy

Thin basement membrane nephropathy (TBMN) is characterized clinically by persistent hematuria, minimal proteinuria, normal renal function, another family member with hematuria, and a benign course. Especially in childhood TBMN, proteinuria of any degree is reported to be uncommon. We report on a boy with benign familial hematuria found by urinary screening at 3 years of age who presented with nephrotic syndrome (NS) at 15 years of age. His renal histology showed TBMN associated with minimal change disease (MCD). Treatment with corticosteroid resulted in complete remission of NS in a short period of time, while isolated hematuria persisted during the follow-up period despite this therapy. We speculate, therefore, that the nephrotic range proteinuria is not due to TBMN but rather is the manifestation of associated MCD. Several cases of TBMN with NS have been reported in adults, but it has not yet been reported in children in the literature. To our knowledge, this is the first case of childhood TBMN associated with NS resulting from coincidental MCD.

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.

Glomerular basement membrane thickness in children: a stereologic assessment

BACKGROUND

Stereologic methods have emerged as the technique of choice in assessing glomerular basement membrane (GBM) thickness, following conceptual modeling comparing the stereologic technique of harmonic mean of the orthogonal intercept estimation (Th) with the model based method of arithmetic mean estimation (ATH), with no direct comparison undertaken. We undertook to establish the gold standard for GBM estimation and use this technique to establish a range for GBM thickness in children.

METHODS

Intra-observer and inter-glomerular variation was estimated in 34 cases with (presumed) normal GBM thickness, using Th, ATH and a rapid direct measurement technique, with intra-observer variation measured in 35 cases with GBM attenuation. A total of 34,011 measurements were undertaken to establish a range for Th in children on 212 biopsies from 199 patients (127 male) demonstrating minimal change nephropathy (N = 153), focal segmental glomerulosclerosis (24), no abnormality (24), and acute tubular necrosis (8), which were used as surrogates for normals.

RESULTS

Th demonstrated less variation than ATH in both the normal and attenuated groups. GBM thickness increased throughout childhood, from 194 +/- 6.5 nm (mean +/- SE) at one year to 297 +/- 6.0 nm at 11 years, with a reduced rate of increase after age 11 years.

CONCLUSION

Stereologic methods are superior to model based techniques in estimating GBM thickness and should be regarded as the technique of choice in this area. GBM thickness was observed to increase during childhood with no gender effect demonstrable as a main effect or interaction.

Thin basement membrane disease and acute renal failure secondary to gross hematuria and tubular necrosis

A patient with thin basement membrane disease (TBMD), macroscopic hematuria, and acute renal failure is described. A renal biopsy showed massive occlusion of renal tubules by red blood cells and casts. This was accompanied by tubular cell damage consistent with acute tubular necrosis. The patient was receiving warfarin because of a history of deep venous thrombosis at the time he developed the acute renal failure. The possible relationship of the warfarin therapy to the TBMD, intratubular hemorrhage, and acute renal failure are discussed.

Immunohistochemical study of alpha 1-5 chains of type IV collagen in hereditary nephritis

The distribution of alpha 1-5 chains of type IV collagen [alpha 1-5(IV)] in the glomerular basement membrane (GBM) and epidermal basement membrane (EBM) of 23 families with hereditary nephritis was examined by indirect immunofluorescence. These families were divided into three clinicopathological groups. Group I (10 families) patients showed a widespread "basket weave" pattern of the GBM and a family history of nephritis was present. Group II (6 families) patients showed a widespread "basket weave" change without a family history of nephritis. Group III (7 families) patients showed a widespread attenuation of the GBM but no "basket weave" change, and had a family history of nephritis and chronic renal failure. alpha 1(IV) and alpha 2(IV) were present in all affected and unaffected family members and controls. All normal family members and controls expressed alpha 3(IV), alpha 4(IV) and alpha 5(IV) in the GBM and alpha 5(IV) in the EBM in a diffuse pattern. All group I families and three of the group II families exhibited complete loss of the alpha 5(IV) antigen from the GBM and EBM in male patients, and segmental loss of the alpha 5(IV) antigen in female patients. In these families the alpha 3(IV) and alpha 4(IV) antigens were completely lost from the GBM in male patients with severe nephritis, whereas alpha 3(IV) alpha 4(IV) were present but diminished in male patients with mild nephritis. Three group II and all group III families expressed the alpha 3-5(IV) antigens in an identical manner to that of normal controls. These findings indicate that the heterogeneity of hereditary nephritis reflects a variety of aberrant expression patterns of alpha 3-5(IV) and that immunohistochemical examination of alpha 5(IV) in the EBM is a useful method for the diagnosis of X-linked 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)

The association of IgA glomerulonephritis and thin glomerular basement membrane disease in a hematuric patient: light and electron microscopic and immunofluorescence investigation

A double glomerulopathy (IgA glomerulonephritis [IgAGN] associated with thin glomerular basement membrane disease [TGBMD]) is reported in a 39-year-old woman presenting with macroscopic-microscopic hematuria. Her 3-year-old daughter was also affected by microhematuria of probable glomerular origin. The diagnosis of IgAGN was made by means of immunofluorescence investigation, which showed generalized diffuse mesangial deposits. TGBMD was identified by electron microscopic investigations, which disclosed thinning (up to 160 nm) of basement membrane of several capillary loops and prominence of the lamina densa. Bearing in mind the known frequencies of the two glomerulopathies, their association may not be coincidental, and, therefore, is worthwhile researching in hematuric patients.

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.

Afferent arteriolar C3 disease--a distinct pathological entity

Afferent arteriolar C3 deposition was the sole histological abnormality in 79 and the major histological abnormality in an additional 39 of 959 renal biopsies performed over a 10-year period. Of these 79 patients, hematuria was the presenting symptom in 90%, with coincident loin pain in 49%. Urine microscopy of asymptomatic first-degree relatives revealed hematuria in 44% of children and siblings and 54% of parents, suggesting autosomal dominant inheritance. Arteriolar C3 deposition was confirmed by biopsy in four asymptomatic relatives with hematuria. Generalized thinning of glomerular basement membrane (less than 200 nm) was observed in five patients and focal thinning was observed in six patients with coincident afferent arteriolar C3 deposition. Seven other patients were identified as having generalized thinning of glomerular basement membrane in the absence of afferent arteriolar C3 deposition. Renal function was stable and similar in all groups studied over 37.9 +/- 23.7 months. No difference in clinical presentation or urinary abnormalities was evident between the groups. No arteriolar C3 deposition was evident in eight autopsy specimens with no known renal disease. It was concluded that afferent arteriolar C3 deposition is a marker of a distinct hereditary pathological entity, with differentiation from thin basement membrane disease not possible on clinical grounds. The medium- and long-term prognoses with respect to renal function are excellent.

Glomerular basement membrane thickness in children. A morphometric study

Measurements of glomerular basement membrane (GBM) thickness in children with minimal change nephrotic syndrome were made on electron micrographs of 43 biopsy specimens obtained from 35 children aged 1-13 years, of whom 13 were in remission at the time of biopsy. Measurements were also made in 2 children with non-glomerular disorders. A mean of 189 measurements per biopsy were made, using prints of x6,400-12,000 magnification. Quadratic curves were fitted by regression analysis to the mean GBM thickness for each of the 35 initial nephrotic biopsies, plotted against age for the whole group and separately for sex, race and the presence or absence of proteinuria at the time of biopsy. There were no significant differences in race or proteinuria, but there was a trend towards a thicker GBM in young males which disappeared by 9 years of age. From the mean +/- 2 SD of GBM thickness for each of the 35 initial nephrotic biopsies the calculated thickness ranged from 100-340 nm at 1 year of age to 190-440 nm at 9 years of age and older. The growth curve for GBM thickness increases steeply initially, reaching a plateau at 9 years of age. Because there was no significant difference between proteinuric patients and those in remission, while measurements in the nephrotic syndrome and non-glomerular disorders closely agreed, we believe that our results demonstrate the normal GBM thickness and growth pattern.

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.

Mesangial changes in IgA nephropathy in children

The mesangial changes in 92 renal biopsy specimens from 81 children with IgA nephropathy were correlated with the clinical and the other renal biopsy findings. Three types of mesangial changes were identified: mesangial hypercellularity was predominant compared with the increase in matrix in 34 biopsy specimens (type A), the degrees of mesangial hypercellularity and matrix increase were similar in 36 (type B) and matrix increase was predominant in 22 (type C). The interval between the onset of disease and biopsy was significantly shorter in biopsies with type A mesangial changes (P less than 0.01) and significantly longer in those with type C (P less than 0.01). Serial pathologic observations revealed that predominant mesangial hypercellularity was almost exclusively seen in the initial biopsy but predominant matrix increase was usually seen in the follow-up biopsy. The percentage of glomeruli showing sclerosis was significantly higher in biopsies with type C mesangial changes (P less than 0.05). At the latest follow-up, 58% of the patients showing type A and 57% showing type B lost their proteinuria, whereas only 9% showing type C lost their proteinuria (P less than 0.01). These findings suggest that predominant mesangial hypercellularity is characteristic of the early lesion of childhood IgA nephropathy, and progression of disease leads to gradual decrease of mesangial cellularity and increase of matrix with sclerosis.

Nonfamilial hematuria associated with glomerular basement membrane alterations characteristic of hereditary nephritis: comparison with hereditary nephritis

Characteristic ultrastructural alterations of the glomerular basement membrane (GBM) have been reported in hereditary nephritis and in children without a family history of renal disease. The clinical features, renal biopsy findings, and subsequent course were studied retrospectively in 48 children with such GBM changes to compare findings in those with and without a family history of nephritis and to determine the significance of the GBM changes in patients with nonfamilial disease. All 48 patients had hematuria. For 30, there was hematuria in at least one other member of the family (familial hematuria group); for 18, there was no familial incidence. There were no differences between the two groups with regard to clinical and pathologic findings. At the latest follow-up six boys with familial hematuria and three boys with nonfamilial hematuria had reduced renal function, and nine boys with familial hematuria and four boys and one girl with nonfamilial hematuria had neurosensory deafness. Our study results show that children with these GBM changes, with or without a family history of hematuria, tend to have a progressive course, with frequent occurrence of neurosensory deafness, and that the prognosis is more severe in boys. These observations suggest that such GBM changes in patients with nonfamilial hematuria may represent new mutations for hereditary nephritis.

Alport's syndrome: specificity and pathogenesis of glomerular basement membrane alterations

In Alport's syndrome (AS) thinning and splitting of the glomerular basement membrane (GBM) are assumed to be characteristic ultrastructural alterations. Both lesions are, however, non-specific because they can occur in other glomerulopathies. In addition, splitting may be found in non-glomerular structures. It should be emphasized that the characteristic lesion in AS is a result of the widespread combination of thin and split GBM in the same biopsy specimen. In our opinion the basic lesion is the thin GBM, which is characterized by a lamina densa (measuring 50-150 nm in thickness) which may begin to split as a result of focal detachment of podocyte pedicles (spacing) and repeated subepithelial deposition of new lamina densa layers. Splitting thus appears to be a secondary lesion. Thinning of GBM may represent a persistent embryonal status of the lamina densa and may thus be the result of a development defect. This assumption is supported by the findings of fetal-like glomeruli and small capillary loops in AS.

Clinical course of immunoglobulin A nephropathy in children

The clinical presentation, initial laboratory and renal biopsy findings, and subsequent clinical course of IgA nephropathy were studied retrospectively in 200 children, and findings in those with younger onset and older onset were compared. Eighty-three patients were 8 years of age or younger (group 1) and 117 were 9 years of age or older (group 2) at onset. There were no differences between the two groups with regard to sex, initial renal function, incidence of hypertension and macroscopic hematuria, degree of proteinuria, and pathologic findings. At the latest follow-up, two patients in group 1 and eight in group 2 had chronic renal failure, and five patients in group 1 and 21 in group 2 had heavy proteinuria with or without hypertension (P less than 0.01), whereas 36 (43%) patients in group 1 and 29 (25%) in group 2 had normal urine, blood pressure, and glomerular filtration rate (P less than 0.01); the disease followed a significantly more benign course in children with younger onset than in those with older onset. These observations suggest some age-related differences in the natural history of childhood IgA nephropathy.

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 and lamina densa in infants and children: an ultrastructural evaluation

The glomerular basement membrane and lamina densa are complex structures that change in composition and thickness with age. We studied their ultrastructural morphology in 37 infants and children, from 1 day to 11 years of age, who died without clinical or morphological evidence of renal disease. The glomerular basement membrane and its lamina densa rapidly increase in width during the first 2 years of life, followed by continued, albeit slower, growth during later childhood.

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.

Focal segmental glomerulosclerosis with and without nephrotic syndrome in children

The clinical presentation, initial laboratory and renal biopsy findings, and course of focal segmental glomerulosclerosis (FSGS) were studied retrospectively in 57 children in order to compare findings in those with and without nephrotic syndrome and to establish factors of prognostic significance. All patients had proteinuria. Eleven patients were otherwise asymptomatic, and nephrotic syndrome did not develop (group 1); 14 patients had asymptomatic proteinuria, but nephrotic syndrome subsequently developed (group 2); 32 patients had nephrotic syndrome (group 3). There were no differences between these three groups with regard to sex, age, initial renal function, incidence of hypertension and hematuria, and pathologic findings. At the latest follow-up, five group 1 patients, six in group 2, and 14 in group 3 had chronic renal failure; the incidence was similar for those with asymptomatic proteinuria and those with nephrotic syndrome. The location of the sclerosis within the glomerulus proved to have prognostic significance. All 12 patients with peripheral FSGS maintained normal renal function, whereas in 25 of the 44 with hilar FSGS chronic renal failure developed.

Glomerular electron-dense deposits in childhood IgA nephropathy

An electron-microscopic study of the glomeruli was made on 154 children with IgA nephropathy and no evidence of systemic disease, in whom immunofluorescence microscopy had shown diffuse mesangial deposition of IgA. Mesangial deposits were observed in all but eight children. Subepithelial deposits were observed in 40 children and were almost always accompanied by both mesangial and subendothelial deposits. Subepithelial deposits were significantly associated with more severe clinical presentations, a worse outcome and more severe light microscopic glomerular changes. These observations support the concept that IgA nephropathy is an immune complex disease.