A Japanese family with Alport syndrome associated with esophageal leiomyomatosis: genetic analysis of COL4A5 to COL4A6 and immunostaining for type IV collagen subtypes

BACKGROUND: In some families, X-linked Alport syndrome (AS) is associated with diffuse leiomyomatosis. We describe clinical, pathologic and molecular-genetic findings in a Japanese family with this inheritance mode of AS in association with leiomyomatosis. PATIENT: AS was diagnosed in a one-year-old boy with recurrent aspiration pneumonia caused by esophageal stenosis from leiomyomatosis. Diagnosis was confirmed by electron microscopy coupled with type IV collagen chain subtype staining in a renal biopsy specimen. His mother, who exhibited esophageal leiomyomatosis and is heterozygous for AS, showed a discontinuous staining pattern for collagen alpha5(IV) chain along the epidermal basement membrane in a skin biopsy specimen. Genetic analysis in the boy revealed the deletion of the first two exons of COL4A6 together with deletion of the 5' end of COL4A5. Despite administration of cyclosporin A, massive proteinuria has persisted in the boy, although renal function otherwise remains normal. CONCLUSION: Identification of an AS patient during infancy is extremely rare. Clinical manifestations, including macroscopic hematuria, cataracts and leiomyomatosis caused by the large deletion involving COL4A5 to COL4A6, led to early presentation with AS.     

Mutation detection of COL4An gene based on mRNA of peripheral blood lymphocytes and prenatal diagnosis of Alport syndrome in China

Aim: Alport syndrome (AS) is a progressive renal disease characterized by haematuria and progressive renal failure. An accurate genetic diagnosis of AS is very important for genetic counselling and even prenatal diagnosis. Methods: We detected mutation of COL4An by amplifying the entire coding sequence mRNA of peripheral blood lymphocytes using polymerase chain reaction (PCR) in five Chinese AS families who asked for genetic counselling and prenatal diagnosis, then performed prenatal genetic diagnosis for four families. Mutation analysis of the foetus was made using DNA extracted from amniocytes. Foetus sex was determined by PCR amplification of SRY as well as karyotype analysis. Maternal cell contamination was excluded by linkage analysis. Results: Four different COL4A5 gene variants and two COL4A3 gene variants were detected in the five families. Because there was a de novo mutation in family 2, prenatal diagnosis was performed for the other four families. Results showed a normal male foetus for family 1 and family 4, respectively. Results showed an affected male foetus for families 3 and 5, and the pregnancies were terminated. Conclusion: An easier, faster and efficacious method for COL4An gene mutation screening based on mRNA analysis from peripheral blood lymphocytes was established. Prenatal genetic diagnosis was performed in four AS families in China.     

Attitudes toward genetic diagnosis and prenatal diagnosis of X-linked Alport syndrome in China

Aim: Alport syndrome (AS) is a progressive renal disease characterized by hematuria and progressive renal failure. X‐linked dominant AS (XLAS) is the predominant inheritance form caused by mutations in COL4A5 gene. Attitudes toward genetic diagnosis and prenatal diagnosis for Chinese AS families were investigated. Attitudes toward genetic diagnosis and prenatal diagnosis in Chinese XLAS families were evaluated in the current study. Methods: A total of 160 XLAS patients and their 126 healthy family members in China were interviewed. After providing background knowledge counselling and education on AS, their attitudes toward genetic diagnosis and prenatal diagnosis were evaluated by multiple‐choice questionnaire. Results: Majority of the respondents cared mostly about the prognosis and treatment effects of AS (89.9% vs 81.1%) since they considered that the worst outcome of XALS was renal insufficiency (92.3%). Of all the interviewees, 99.3% were interested in genetic research for the discovery of better treatments and more appropriate diagnostic tools (positive attitudes) (89.5% vs 73.2%). About 80% of the participants would accept prenatal testing and subsequent termination of pregnancy in cases of affected foetuses (boys: 86.8% and girls: 74.6%, respectively). Conclusion: Most Chinese XLAS families show positive attitudes and desire new discoveries in treatment and diagnosis. About 80% of respondents would approve prenatal testing with a desire for selective termination of pregnancy rather than predicting the health of a future child.     

Successful renal transplantation in a family with a novel mutation in COL4A3 gene and autosomal recessive Alport syndrome

Alport syndrome (AS) is an inherited disorder of basement membranes caused by mutations affecting specific proteins of the type IV collagen family, presenting with nephropathy and extrarenal manifestations such as sensorineural deafness and ocular anomalies. Ten percentage to 15% of the patients with AS have autosomal recessive (ARAS) due to mutation in either COL4A3 or COL4A4 gene. We report a novel mutation in the COL4A3 gene in an Indian family with ARAS. The above‐mentioned genetic anomaly was a missense variation in exon 26 of the COL4A3 gene (chr2:228137797G>A; c.1891G>A) that resulted in the amino acid substitution of Arginine for Glycine at codon 631 (p.Gly631Arg) that was present in the heterozygous state in the asymptomatic parents and homozygous state in the male offspring who presented with early‐onset end‐stage renal disease, lenticonus and hearing loss. The patient (male offspring) underwent successful renal transplantation with his mother as a donor.     

Alport综合征精准诊治进展

Alport综合征是由于编码Ⅳ型胶原α3/α4/α5链的基因突变导致的遗传性肾脏疾病,临床上表现为血尿、蛋白尿及进行性肾衰竭,部分患者合并耳聋和眼部改变。随着医学技术的进步,Alport综合征的诊断逐渐精确,诊断依据从最初的临床表现,到肾组织电镜典型的肾小球基底膜病理改变,再到目前广泛应用的基因突变检测。目前认为Alport综合征是可以治疗的疾病,尽早应用血管紧张素转换酶抑制剂(ACEI)和血管紧张素受体阻滞剂(ARB)可以推迟Alport综合征肾衰竭发生。     

Sporadic case of X-chromosomal Alport syndrome in a consanguineous family

Alport syndrome (AS) is a genetic disorder of basement membranes caused by mutations in type IV collagen genes that is characterized by chronic hematuria and progressive nephropathy leading to renal failure. The main extrarenal features include sensorineural hearing loss and ocular lesions. The mode of inheritance is X-linked dominant in about 80%–85% of the affected families, whereas autosomal transmission is rarely encountered. We report a male patient originating from a healthy consanguineous Lebanese family who presented with an unusual association of obstructive uropathy and AS. Hematuria and proteinuria were initially attributed to a suspected poststreptococcal glomerulonephritis (GN) and high-grade subpelvic ureteral stenosis. Persistence of symptoms after medical treatment of poststreptococcal GN and surgical correction of obstructive uropathy finally led to renal biopsy. The observed ultrastructural changes of the glomerular basement membrane were typical for AS.Molecular genetic studies revealed a previously undescribed de novo mutation in the COL4A5 gene, excluding maternal heterozygotic carrier status. This case report emphasizes the importance of hereditary nephritis in the differential diagnosis of chronic hematuria, and demonstrates the value of molecular studies for genetic counselling in AS. Received: 9 October 1998 / Revised: 15 February 1999 / Accepted: 24 August 1999     

Alport syndrome associated with diffuse leiomyomatosis: COL4A5-COL4A6 deletion associated with a mild form of Alport nephropathy.

BACKGROUND: The X-linked Alport syndrome (AS) is an inherited nephropathy due to mutations in the COL4A5 gene, encoding the alpha5 chain of type IV collagen, a major component of the glomerular basement membrane (GBM). Here, we report a new kindred with the rare association of X-linked AS and diffuse leiomyomatosis (DL), which is a tumourous process involving smooth muscle cells of the oesophagus, the tracheobronchial tree and, in females, the genital tract. For this syndrome, an almost constant association of large COL4A5 rearrangements with a severe juvenile form of nephropathy has been described for male patients. METHODS: DNA rearrangement at the COL4A5-COL4A6 locus was studied in several members of this family using polymerase chain reaction and pulsed field gel electrophoresis. Furthermore, immunohistochemical staining of tumour and skin samples was performed. RESULTS: The affected patients in this family carry a 120 kb deletion by which the COL4A5 exon 1 and COL4A6 exons 1, 1', and 2 are removed. Immunohistochemical investigation of a skin biopsy of an affected male patient confirmed the absence of both the alpha5 and the alpha6 chains of type IV collagen in the basement membrane of the skin. Surprisingly, both affected male patients had a rather mild renal phenotype. CONCLUSIONS: This report shows that, contrary to what has been reported to date, patients suffering from AS associated with DL can be associated with a late onset renal failure (adult) form of nephropathy.     

Successful renal transplantation in Jeune syndrome type 2

Jeune syndrome (asphyxiating thoracic dystrophy) is a rare inherited disease which is fatal in early childhood in 70% of cases. Severe renal involvement may occur and lead to chronic renal insufficiency in patients who survive respiratory failure. Therefore the opportunity to perform kidney transplantation is quite rare. We report a successful cadaver renal transplantation in a 10-year-old boy with Jeune syndrome type 2. Received August 20, 1997; received in revised form and accepted December 5, 1997     

A novel G472R mutation in a Turkish family with X-linked Alport syndrome

Alport syndrome (AS) is a hereditary disorder of progressive nephritis. Most cases are X-linked, but autosomal forms have been reported. The X-linked form is associated with mutations in the COL4A5 gene that encodes the α5 chain of type IV collagen. More than 200 mutations have been reported in X-linked AS. We report a novel 1616 G>A mutation resulting in glycine substitution to arginine at position 472 in a Turkish family with a severely affected man and several variably affected women. This is the first Turkish family in whom the molecular basis of the disease has been reported. Received: 16 December 1998 / Revised: 30 June 1999 / Accepted: 7 July 1999     

Type-IV collagen related diseases

Alport syndrome (ATS) is a progressive inherited glomerulonephritis accounting for 1-2% of all patients who start renal replacement therapy, with an estimated gene frequency of approximately 1 in 5000. ATS is a genetically heterogeneous disease, commonly inherited as an X-linked semi-dominant trait, caused by mutations in COL4A5, on the X-chromosome, and only rarely (less than 10% of cases) caused by the COL4A3 or the COL4A4 gene on chromosome 2q. In the X-linked form females are generally less affected than males, microhematuria being the only sign present throughout life, although approximately 30% can progress to end-stage renal disease. It became evident in recent years that mutations in the COL4A3 or the COL4A4 gene can give rise not only to autosomal recessive ATS syndrome, in which males and females are severely affected, but also to an autosomal dominant form, where the clinical progression towards impaired renal function can be very slow and also to benign familial hematuria (BFH) in which renal function is preserved.     

Clinical spectrum of Denys-Drash and Frasier syndrome

Denys-Drash syndrome (DDS) and Frasier syndrome (FS) are two related conditions caused by mutations of the Wilms tumor gene, WT1. Both syndromes are characterized by male pseudohermaphroditism, a progressive glomerulopathy, and the development of genitourinary tumors. DDS and FS have previously been distinguished by differences in nephropathy, with DDS patients demonstrating diffuse mesangial sclerosis (DMS) in contrast to focal and segmental glomerulosclerosis (FSGS) in FS patients. The clinicopathological features and genotype analysis of two patients with WT1 mutations are presented in this report. Genotype analysis of the first patient revealed a previously undescribed mutation in exon 8 of the WT1 gene. The second patient presented with a rapidly progressive nephropathy characterized histologically by DMS, but was found to have the genetic mutation seen in FS patients. A summary of all reported patients with the characteristic mutation associated with FS demonstrates the clinical overlap of this syndrome with DDS. This suggests that both these conditions should be considered as part of the spectrum of disease due to WT1 gene mutations rather than as separate diseases. Clinical classification remains important for prognosis, as the underlying renal disease appears to predict the progression of nephropathy independently of the genetic abnormality.     

Autosomal recessive Alport syndrome: linkage analysis and clinical features in two families.

BACKGROUND: Genetic heterogeneity is a well-known feature of Alport syndrome (AS). Most families with AS show an X-linked dominant pattern of inheritance but about 15% of families show an autosomal inheritance of the disease. Autosomal recessive AS may account for 10% of the total number of cases and is caused by mutations in the COL4A3 and COL4A4 genes. The clinical spectrum of this rare disorder has not been well clarified. METHODS: We present two families with AS. Two affected members of these families have entered end-stage renal disease (ESRD) in their 30s, and the other three are older than 15 years and have normal serum creatinine. Four of the five patients have deafness but none have ocular abnormalities. Two have been transplanted and have not suffered from anti-GBM antibody nephritis. Men and women are equally affected. We have performed linkage analysis for chromosome 2 with the following markers: D2S279, COL4A3/4 DNTR, COL4A4 RFLP Hae III. RESULTS: We demonstrate that both families, one of them consanguineous, are linked to the COL4A3/4 locus. CONCLUSIONS: We can conclude that the only significant difference between the X-linked and the autosomal recessive forms of AS lies in the fact that in the latter females are as affected as males; thus the idea that autosomal recessive AS causes ESRD during childhood must be discarded. Other clinical features such as age of deafness or the presence of post-transplant anti-GBM antibody nephritis show no differences between the entities. Thus an accurate familial study is mandatory in patients with AS, as the identification of the different patterns of inheritance may cause a great difference in genetic counselling. Linkage analysis is the only effective molecular diagnosis that can be performed nowadays.     

Identification of COL4A5 defects in Alport's syndrome by immunohistochemistry of skin

BACKGROUND: The COL4A3-COL4A4-COL4A5 network in the glomerular basement membrane is affected in the inherited renal disorder Alport's syndrome (AS). Approximately 85% of the AS patients are expected to carry a mutation in the X-chromosomal COL4A5 gene and 15% in the autosomal COL4A3 and COL4A4 genes. The COL4A5 chain is also present in the epidermal basement membrane (EBM). It is predicted that approximately 70% of the COL4A5 mutations prevent incorporation of this chain in basement membranes. METHODS: We investigated whether or not COL4A5 defects could be detected by immunohistochemical analysis of the EBM. Punch skin biopsies were obtained from 22 patients out of 17 families and two biopsy specimens from healthy males were used as controls. RESULTS: In four cases with the COL4A5 frameshift or missense mutations, the COL4A5 chain was either lacking from the EBM (male) or showed a focally negative pattern (female). In three other patients with a COL4A5 missense mutation, a COL4A3 and a COL4A4 mutation, respectively, the COL4A5 staining was normal. A (focally) negative EBM-COL4A5 staining was found in three patients of six families with a diagnosis of AS and in one family of a group of four families with possible AS. CONCLUSIONS: The (focal) absence of COL4A5 in the EBM of skin biopsy specimens can be used for fast identification of COL4A5 defects. Combined with polymorphic COL4A5 markers, both postnatal and prenatal DNA diagnosis are possible in the family of the patient.     

Diagnosis of Alport syndrome without biopsy?

Alport syndrome (AS) is genetically heterogeneous. The gene COL4A5 is mutated in the more frequent X-linked dominant form of the disease whereas COL4A3 or COL4A4 are mutated in the autosomal recessive and dominant forms. Diagnosis of AS and determination of the mode of transmission are important because of the differences in prognosis and genetic counselling attached to these different forms. Recently, promising results have been obtained in Col4a3-null mice, an animal model for AS, with different therapeutic trials when administered early in the course of the disease, an additional reason for making early diagnosis of AS in children. Since the identification of the molecular basis of the disease, mutation screening is theoretically the best diagnostic approach, avoiding the use or renal or skin biopsy. However, for many reasons linked to the genetic heterogeneity of the disease, the large size of the three genes and the random distribution of the mutations all along these huge genes, this method is tedious, expensive and time consuming. Moreover, its sensitivity is reduced. For these reasons, evaluation of the expression of type IV collagen chains in the skin, and if necessary in the renal basement membrane, remains a useful tool for AS diagnosis. At this time, the indication for these different approaches, which are not mutually exclusive but complementary, depends on the patient clinical presentation and family history.     

Phenotypic and genotypic features of Alport syndrome in Chinese children

Chinese Alport syndrome (AS) was analyzed in 44 unrelated patients who were screened for mutations in the COL4A5 gene by polymerase chain reaction (PCR)-single-strand conformation polymorphism analysis or PCR direct sequencing in 30 of the 44 patients. The clinical data showed that all patients had hematuria; 25 of 29 male patients (86%) and 9 of 15 female patients (60%) had proteinuria; 11 of 29 male patients (38%) and 1 of 15 female patients (7%) had nephrotic-level proteinuria; 10 of 21 male patients examined (48%) and 1 of 12 female patients examined (8%) had hearing abnormalities. Renal function remained normal despite hearing abnormalities, and ocular lesions occurred in 10%. Among 30 of 44 patients who had a family history of end-stage renal disease (ESRD), 80% (24/30) belonged to X-linked juvenile kindreds, and 20% (6/30) patients to adult kindreds. Of the 44 patients, 14 did not have a family history of ESRD, while 11 of 14 patients diagnosed with X-linked AS did. DNA analysis revealed four missense mutations, two silent mutations, one substitution, and one in-frame deletion. PCR along with Southern hybridization analysis revealed a large deletion of the paired COL4A5 and COL4A6 genes. Chinese AS patients were characterized clinically with hematuria, heavy proteinuria, and more juvenile forms. Mutations in these patients were usually small mutations, while a large deletion involving the 5' part of both COL4A5 and COL4A6 genes was identified.     

The role of discoidin domain receptor 2 in the renal dysfunction of alport syndrome mouse model

Alport syndrome (AS) is a hereditary glomerular nephritis caused by mutation in one of the type IV collagen genes α3/α4/α5 that encode the heterotrimer COL4A3/4/5. Failure to form a heterotrimer due to mutation leads to the dysfunction of the glomerular basement membrane, and end-stage renal disease. Previous reports have suggested the involvement of the receptor tyrosine kinase discoidin domain receptor (DDR) 1 in the progression of AS pathology. However, due to the similarity between DDR1 and DDR2, the role of DDR2 in AS pathology is unclear. Here, we investigated the involvement of DDR2 in AS using the X-linked AS mouse model. Mice were treated subcutaneously with saline or antisense oligonucleotide (ASO; 5 mg/kg or 15 mg/kg per week) for 8 weeks. Renal function parameters and renal histology were analyzed, and the gene expressions of inflammatory cytokines were determined in renal tissues. The expression level of DDR2 was highly elevated in kidney tissues of AS mice. Knockdown of Ddr2 using Ddr2-specific ASO decreased the Ddr2 expression. However, the DDR2 ASO treatment did not improve the proteinuria or decrease the BUN level. DDR2 ASO also did not significantly ameliorate the renal injury, inflammation and fibrosis in AS mice. These results showed that Ddr2 knockdown by ASO had no notable effect on the progression of AS indicating that DDR2 may not be critically involved in AS pathology. This finding may provide useful information and further understanding of the role of DDRs in AS.     

X-linked Alport syndrome: natural history in 195 families and genotype- phenotype correlations in males

Alport syndrome (AS) is a type IV collagen hereditary disease characterized by the association of progressive hematuric nephritis, hearing loss, and, frequently, ocular changes. Mutations in the COL4A5 collagen gene are responsible for the more common X-linked dominant form of the disease. Considerable allelic heterogeneity has been observed. A "European Community Alport Syndrome Concerted Action" has been established to delineate accurately the AS phenotype and to determine genotype-phenotype correlations in a large number of families. Data concerning 329 families, 250 of them with an X-linked transmission, were collected. Characteristics of the 401 male patients belonging to the 195 families with COL4A5 mutation are presented. All male patients were hematuric, and the rate of progression to end-stage renal failure and deafness was mutation-dependent. Large deletions, non-sense mutations, or small mutations changing the reading frame conferred to affected male patients a 90% probability of developing end-stage renal failure before 30 yr of age, whereas the same risk was of 50 and 70%, respectively, in patients with missense or splice site mutation. The risk of developing hearing loss before 30 yr of age was approximately 60% in patients with missense mutations, contrary to 90% for the other types of mutations. The natural history of X-linked AS and correlations with COL4A5 mutations have been established in a large cohort of male patients. These data could be used for further evaluation of therapeutic approaches.