Autosomal dominant polycystic kidney disease types 1 and 2: assessment of US sensitivity for diagnosis

PURPOSE

To estimate the sensitivity and specificity of ultrasonography (US) in the diagnosis of autosomal dominant polycystic kidney disease (ADPKD) types 1 and 2, as compared with those of genetic linkage analysis.

MATERIALS AND METHODS

A renal US and DNA analysis for ADPKD was performed in 319 patients who were at risk, 161 of whom were younger than 30 years, from 54 families with ADPKD. The sensitivity of US for diagnosis was estimated by comparing the US results with genotypes inferred from linkage studies.

RESULTS

The sensitivity of US in individuals younger than 30 years who were at risk was 95% for ADPKD type 1 but only 67% for ADPKD type 2. The sensitivity of US for either ADPKD type 1 or ADPKD type 2 in individuals aged 30 years or older who were at risk was 100%. The overall sensitivity in individuals younger than 30 years was 93%. For both ADPKD types 1 and 2 in all patients, US demonstrated a sensitivity of 97%, a specificity of 100%, and an accuracy of 98%.

CONCLUSION

US is the first-line imaging technique that should be used in the diagnosis of ADPKD. The sensitivity in individuals aged 30 years or older is 100%, but if there is a clinical suspicion of ADPKD type 2 in individuals younger than 30 years, linkage analysis should also be considered.

Influence of the ACE gene polymorphism in the progression of renal failure in autosomal dominant polycystic kidney disease

The recent description of a polymorphism in the gene for angiotensin-converting enzyme (ACE), with the D allele associated with greater plasma levels of ACE, allows us to perform studies of the relationship between this polymorphism and chronic renal diseases in which the renin-angiotensin system could be implicated. We examined 155 patients with autosomal dominant polycystic kidney disease (ADPKD) with linkage to the PKD1 locus. The ACE insertion/deletion (I/D) polymorphism was amplified with the previously published flanking primers, and the polymerase chain reaction product was separated, sized on a 2% agarose gel, and visualized by ultraviolet transillumination. The ACE genotype distributions were 11.6%, 63.8%, and 24.5% for II, ID, and DD, respectively. There were no significant differences among the three genotypes with respect to mean age, sex distribution, and prevalence of hypertension. The ACE genotype distribution in patients with end-stage renal failure at the time of data compilation was similar to that of the entire study population. In the subgroup of patients who received renal replacement therapy before the age of 50 years, we found a significant association between DD genotype and onset of end-stage renal disease (ESRD) before the age of 50 years compared with II and ID (P = 0.017). We calculated the estimated median renal survival time as 51 years for the II genotype, 53 years for the ID genotype, and 48 years for the DD genotype. There were statistically significant differences between DD and ID patients (P = 0.025). In conclusion, we found DD genotype implies a worse renal prognosis based on both the significantly lower median renal survival time and significantly greater percentage of patients who reach ESRD before the age of 50 years, without implying a greater prevalence of hypertension.

A loss-of-function model for cystogenesis in human autosomal dominant polycystic kidney disease type 2

Autosomal dominant polycystic kidney disease (ADPKD) is genetically heterogeneous, with at least three chromosomal loci (PKD1, PKD2, and PKD3) that account for the disease. Mutations in the PKD2 gene, on the long arm of chromosome 4, are expected to be responsible for approximately 15% of cases of ADPKD. Although ADPKD is a systemic disease, it shows a focal expression, because <1% of nephrons become cystic. A feasible explanation for the focal nature of events in PKD1, proposed on the basis of the two-hit theory, suggests that cystogenesis results from the inactivation of the normal copy of the PKD1 gene by a second somatic mutation. The aim of this study is to demonstrate that somatic mutations are present in renal cysts from a PKD2 kidney. We have studied 30 renal cysts from a patient with PKD2 in which the germline mutation was shown to be a deletion that encompassed most of the disease gene. Loss-of-heterozygosity (LOH) studies showed loss of the wild-type allele in 10% of cysts. Screening of six exons of the gene by SSCP detected eight different somatic mutations, all of them expected to produce truncated proteins. Overall, >/=37% of the cysts studied presented somatic mutations. No LOH for the PKD1 gene or locus D3S1478 were observed in those cysts, which demonstrates that somatic alterations are specific. We have identified second-hit mutations in human PKD2 cysts, which suggests that this mechanism could be a crucial event in the development of cystogenesis in human ADPKD-type 2.

Seven novel mutations of the PKD2 gene in families with autosomal dominant polycystic kidney disease

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is genetically heterogeneous, with at least three chromosomal loci accounting for the disease. Mutations in the PKD2 gene on the long arm of chromosome 4 are expected to be responsible for approximately 15% of cases of ADPKD.

METHODS

We report a systematic screening for mutations covering the 15 exons of the PKD2 gene in eight unrelated families with ADPKD type 2, using the heteroduplex technique.

RESULTS

Seven novel mutations were identified and characterized that, together with the previously described changes, amount to a detection rate of 85% in the population studied. The newly described mutations are two nonsense mutations, a 1 bp deletion, a 1 bp insertion, a mutation that involves both a substitution and a deletion (2511AG-->C), a complex mutation in exon 6 consisting of a simultaneous 7 bp inversion and a 4 bp deletion, and the last one is a G-->C transversion that may be a missense mutation. Most of these mutations are expected to lead to the formation of shorter truncated proteins lacking the carboxyl terminus of PKD2. We have also characterized a frequent polymorphism, Arg-Pro, at codon 28 in this gene. The clinical features of these PKD2 patients are similar to the previously described, with the mean age of end-stage renal disease being 75.5 years (SE +/- 3.8 years).

CONCLUSIONS

Our results confirm that many different mutations are likely to be responsible for the disease and that most pathogenic defects probably are point or small changes in the coding region of the gene.

Coordinate expression of the autosomal dominant polycystic kidney disease proteins, polycystin-2 and polycystin-1, in normal and cystic tissue

A second gene for autosomal dominant polycystic kidney disease (ADPKD), PKD2, has been recently identified. Using antisera raised to the human PKD2 protein, polycystin-2, we describe for the first time its distribution in human fetal tissues, as well as its expression in adult kidney and polycystic PKD2 tissues. Its expression pattern is correlated with that of the PKD1 protein, polycystin-1. In normal kidney, expression of polycystin-2 strikingly parallels that of polycystin-1, with prominent expression by maturing proximal and distal tubules during development, but with a more pronounced distal pattern in adult life. In nonrenal tissues expression of both polycystin molecules is identical and especially notable in the developing epithelial structures of the pancreas, liver, lung, bowel, brain, reproductive organs, placenta, and thymus. Of interest, nonepithelial cell types such as vascular smooth muscle, skeletal muscle, myocardial cells, and neurons also express both proteins. In PKD2 cystic kidney and liver, we find polycystin-2 expression in the majority of cysts, although a significant minority are negative, a pattern mirrored by the PKD1 protein. The continued expression of polycystin-2 in PKD2 cysts is similar to that seen by polycystin-1 in PKD1 cysts, but contrasts with the reported absence of polycystin-2 expression in the renal cysts of Pkd2+/- mice. These results suggest that if a two-hit mechanism is required for cyst formation in PKD2 there is a high rate of somatic missense mutation. The coordinate presence or loss of both polycystin molecules in the same cysts supports previous experimental evidence that heterotypic interactions may stabilize these proteins.

Mutational analysis within the 3' region of the PKD1 gene

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common genetic diseases in humans, affecting 1 out of 1000 individuals. At least three different genes are involved in this disease. The search for mutations in PKD1 is complicated because most of the transcript is encoded by a genomic region reiterated more proximally on chromosome 16, and no prevalent mutation has been reported.

METHODS

We have screened DNA from exon 43 through exon 46 and intron 40 of the PKD1 sequence by single-stranded conformational polymorphism (SSCP) analysis in 175 ADPKD patients.

RESULTS

We have found 25 differences with respect to the reported PKD1 DNA sequence, seven of which are mutations (Q4041X, Q4124X, IVS44-1G-->C, IVS45-1G-->A, 12801del28, R4275W, and Q4224P). We found different phenotypical expressions of the same mutation in the families studied. We have detected several common polymorphisms, and some of them cosegregate, suggesting a common origin of these alleles in PKD1.

CONCLUSIONS

The detection of only seven mutations in 175 unrelated ADPKD patients for this region of the PKD1 analyzed suggests that mutations could be widespread throughout all of the gene and that a prevalent mutation is not expected to occur. The identified PKD1 missense mutations may help to refine critical regions of the protein. Until a quicker and more sensitive method for the detection of mutations becomes available, linkage studies will continue to be the basis for the molecular diagnosis of ADPKD families.

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.

Comparison of phenotypes of polycystic kidney disease types 1 and 2. European PKD1-PKD2 Study Group

BACKGROUND

Although autosomal dominant polycystic kidney disease type 2 (PKD2) is known to have a milder clinical phenotype than PKD1, neither disorder has been compared with an unaffected control population in terms of survival. We report the findings of a multicentre survey that aimed to define more precisely the survival and clinical expression of PKD1 and PKD2.

METHODS

Clinical data from 333 people with PKD1 (31 families) were compared with data from 291 people with PKD2 (31 families) and 398 geographically matched controls. Survival analysis was used to compare age-at-event data. Differences in the prevalence of complications were assessed by logistic regression.

FINDINGS

Median age at death or onset of end-stage renal disease was 53.0 years (95% CI 51.2-54.8) in individuals with PKD1, 69.1 years (66.9-71.3) in those with PKD2, and 78.0 years (73.8-82.2) in controls. Women with PKD2 had a significantly longer median survival than men (71.0 [67.4-74.8] vs 67.3 [64.9-69.7] years), but no sex influence was apparent in PKD1. Age at presentation with kidney failure was later in PKD2 than in PKD1 (median age 74.0 [67.2-80.8] vs 54.3 [52.7-55.9] years). PKD2 patients were less likely to have hypertension (odds ratio 0.25 [95% CI 0.15-0.42]), a history of urinary-tract infection (0.50 [0.31-0.83]), or haematuria (0.59 [0.35-0.98]).

INTERPRETATION

Although PKD2 is clinically milder than PKD1, it has a deleterious impact on overall life expectancy and cannot be regarded as a benign disorder.

Facilitated diagnosis of the contiguous gene syndrome: tuberous sclerosis and polycystic kidneys by means of haplotype studies

Tuberous sclerosis (TSC) and autosomal dominant polycystic kidney disease (ADPKD) are genetically heterogeneous diseases. The major gene for ADPKD (PKD1) lies adjacent to the TSC2 gene on chromosome 16p13. Some reports in the literature referred to an unusual presentation of TSC with enlarged cystic kidneys at birth, but it was not until the localization of the TSC2 and PKD1 genes that it was possible to analyze the interaction between both genes. We describe a case of a child with TSC and enlarged cystic kidneys. The study of genetic marker segregation in the family pointed to the presence of a deletion involving the 3' region of PKD1. A further study of the region showed a deletion of 40 kb involving both PKD1 and TSC2. We suggest that an additive or synergistic effect between PKD1 and TSC2 may cause this renal phenotype. A contiguous gene syndrome involving PKD1 and TSC2 should be suspected in children with TSC and enlarged polycystic kidneys at birth. The first approach to identify a deletion of both genes could be the analysis of the segregation of PKD1 and TSC2 markers in the family.

[Clinical, genetic and molecular studies on autosomal dominant polycystic kidney disease]

BACKGROUND

Two genes causing autosomal dominant polycystic kidney disease (ADPKD), PKD1 and PKD2, have been described. In the present work we study, by means of linkage analysis, the genetic heterogeneity in our population as well as the clinical differences between PKD1 and PKD2.

SUBJECTS AND METHODS

316 subjects belonging to 49 unrelated ADPKD families have been studied by means of 3 microsatellites for PKD1 and 3 for PKD2 to differentiate if they have ADPKD type 1 or 2. The techniques used to analyze the microsatellites have been the chemiluminescence and the silver satining techniques. All the subjects underwent a complete physical examination and a sonographic scan. Clinical and molecular results have been correlated.

RESULTS

Genetic heterogeneity has been proved, with 85% of families linked to PKD1 and 15% to PKD2. The disease is more severe in PKD1, with an earlier age at diagnosis (27.4 vs. 41.4 years; p = 0.0002), a younger age at the onset of end stage renal disease (53.4 vs. 72.7 years, p < 0.00001), and earlier age at diagnosis of hypertension (34.8 vs. 49.7 years; p = 0.001) and a higher prevalence of hypertension for all groups of age. In both forms of ADPKD there were families showing anticipation (8/44 for PKD1 and 2/5 for PKD2) but this was not a widespread phenomenon. Our data do not support the phenomenon of genetic imprinting for this disease.

CONCLUSION

In the population of Catalonia, Spain, PKD1 accounts for 85% of families with autosomal dominant polycystic kidney disease and PKD2 accounts for the remaining 15%. PKD1 form is more severe than PKD2.

Autosomal dominant polycystic kidney disease with anticipation and Caroli's disease associated with a PKD1 mutation. Rapid communication

Autosomal dominant polycystic kidney disease (ADPKD) is the most common renal hereditary disorder. Clinical expression of ADPKD shows interfamilial and intrafamilial variability. We screened for mutations the 3' region of the PKD1 gene, from exon 43 to exon 46, in a family showing anticipation and Caroli's disease and have found a 28 base pairs deletion in exon 46 (12801del28) and a new DNA variant in exon 43 (12184 C to G conserving Ala 3991) segregating with the disease. The mutation should result in a protein 44 amino acids longer then the wild-type PKD1. This PKD1 mutation manifests as typical adult-onset disease in the father, but in the proband, a 26-year-old man, ADPKD was diagnosed as a newborn and was associated with Caroli's disease at the age of 18 years. A renal biopsy performed in childhood disclosed a predominance of glomerular cysts. Mutation 12801del28 is the first molecular defect associated with Caroli's disease and the PKD1 phenotype. The finding of the same mutation in two different members of the same family with different expression of the disease indicates that the phenotypic variation in ADPKD must be due to modifying factors that may radically affect the course of the disease.

Ultrasonographic study of pancreatic cysts in autosomal dominant polycystic kidney disease

Pancreatic cysts are an uncommon extrarenal clinical feature of autosomal dominant polycystic kidney disease (ADPKD). The prevalence of pancreatic cysts, sonographically assessed in ADPKD and in the different typs of ADPKD (PKD1 and PKD2) has not been reported. We have studied 173 ADPKD patients and 160 non-affected family members and found a prevalence of pancreatic cysts, of 9% in ADPKD patients over 30 years of age. The presence of pancreatic cysts was related to the increasing age, to the female sex and to the type of ADPKD, found exclusively in PKD1 patients. No complications related to pancreatic cysts were recorded. Pancreatic cysts are an unusual feature of ADPKD and do not appear to contribute to morbidity or mortality.

Abdominal aortic aneurysms and autosomal dominant polycystic kidney disease

Although cases of autosomal dominant polycystic kidney disease (ADPKD) associated with abdominal aortic aneurysm have been repeatedly reported in the literature, no systematic studies of the aortas of these patients have been performed. In the study presented here, a sonographic study of the abdominal aorta in 139 ADPKD patients and in 149 healthy family members was carried out. For both groups, an increase in aortic diameter related to age and sex, (being wider in men than women) was found. In ADPKD patients, neither a wider aortic diameter nor a higher prevalence of abdominal aortic aneurysms could be found in any age group. It was concluded that, although these patients are prone to develop aortic aneurysms because of hypertension and associated connective tissue disorders, the presence of abdominal aortic aneurysms should be questioned as a frequent feature of ADPKD.

Linkage, clinical features, and prognosis of autosomal dominant polycystic kidney disease types 1 and 2

Linkage analysis was performed on 49 Catalan families with autosomal dominant polycystic kidney disease obtained via the Nephrology Department and related nephrology centers. A total of 336 subjects, 267 at risk for the disease, were investigated using three microsatellites linked to polycystic kidney disease Type 1 (PKD1) and three microsatellites linked to PKD2. All of the subjects underwent physical and sonographic examination. The results demonstrate locus heterogeneity, with 0.85 as the maximum likelihood for the proportion of families linked to PKD1. All of the remaining families were found to be linked to PKD2. Analysis of clinical data in the PKD1 group (N = 146) versus the PKD2 group (N = 20) showed a milder form of the disease in the latter, with a later age at diagnosis (27.4 versus 41.4 yr, P = 0.0002), later age of onset of ESRD (53.4 versus 72.7 yr, P < 0.0001), later age of diagnosis of hypertension (34.8 versus 49.7 yr, P = 0.001) and lower prevalence of hypertension at younger ages. Sonographic findings did not differ significantly between both groups. Although anticipation was observed in both groups, it did not affect the majority of families. No signs of imprinting were found in this study, and the only gender effect was an earlier age of onset of ESRD in men than in women (49.5 versus 53.1 yr in PKD1, P < 0.01 and 70.57 versus 73.6 yr in PKD2, P = 0.1). Molecular analysis of autosomal-dominant polycystic kidney disease allows presymptomatic diagnosis in individuals younger than age 30, and helps in establishing prognosis.

Renal-hepatic-pancreatic dysplasia: an autosomal recessive malformation

We report two brothers with a cystic malformation of the kidneys, liver, and pancreas. In both cases the malformation was fatal and the children died shortly after birth. The pathological findings, consisting of multicystic dysplastic kidneys, dilated and dysgenetic bile ducts, dilated pancreatic ducts, and polysplenia, correspond to those reported by Ivemark as renal-hepatic-pancreatic dysplasia. Many polymalformation syndromes include cystic affectation of these three organs, so this syndrome could be an isolated entity or a final common pathway of response of these organs to a variety of developmental disturbances, which could also include splenic abnormalities. We propose an autosomal recessive pattern of inheritance for renal-hepatic-pancreatic dysplasia.

Successful pregnancy in a patient with hemolytic-uremic syndrome during the second trimester of pregnancy

BACKGROUND

Hemolytic uremic syndrome (HUS) is a rare, well-characterized complication of the puerperium constituting a cause of acute renal failure after an uncomplicated delivery. However, its presentation during pregnancy is unusual, with only four cases before the 20th week of gestation reported.

CASE

A case of HUS occurred at 18 weeks' gestation. Despite the initial severity of the clinical presentation, therapy, consisting of corticosteroids and plasmapheresis, resulted in complete recovery of renal function, with a rapid improvement in thrombocytopenia and hemolysis. No remarkable events occurred after this episode, and a full-term pregnancy with a normal fetal outcome was achieved.

CONCLUSION

We are aware of no other reports of successful pregnancy after the development of HUS during the first half of pregnancy. This provides evidence that continuation of pregnancy until term is possible. Rapid diagnosis and intensive treatment with plamapheresis, corticosteroids and dialysis, when required, may improve the maternal and fetal prognosis.

Patients with multiple myeloma requiring long-term dialysis: presenting features, response to therapy, and outcome in a series of 20 cases

From January 1982 to December 1993, 30 patients with multiple myeloma (MM) required haemodialysis (HD) at our institution. The subgroup of 20 patients who survived more than 2 months on HD is the subject of this study. Four patients were already on HD, due to previous nephropathy, when MM was diagnosed. 13 patients presented with acute renal failure and were on dialysis from the time of diagnosis. The remaining three cases developed renal failure later in the course of the disease. The objective response rate was 40% (8/20). Only two patients could discontinue HD (one had a late partial recovery and one received a kidney graft). Mean hospitalization per year was 19.3 d. The subgroup of patients who survived < 1 year spent a mean of 38.3 d in hospital. Whereas in the subgroup with a survival > 1 year mean hospitalization days was 9.6 (P < 0.001). The median survival was 20 months and six patients survived for > 3 years. In summary, patients with MM and severe renal failure who survive the first 2 months on dialysis have an objective response rate to chemotherapy of 40% and a median survival of almost 2 years, with 30% long-term survivors.

Pulmonary hemorrhage as a clinical manifestation of hemolytic-uremic syndrome associated with mitomycin C therapy

Mitomycin C (MMC) is an alkylating agent that has been recently associated with the hemolytic-uremic syndrome (HUS). Pulmonary impairment in the HUS is rarely reported in the literature, and no reports of pulmonary hemorrhage, as a clinical feature of the HUS, have been documented. We describe two women who developed HUS after MMC therapy and presented massive pulmonary bleeding. Pulmonary hemorrhage is an uncommon feature in the HUS, and seems to appear especially in the HUS associated with MMC therapy. It is extremely resistant to standard treatment, and confers a poor prognosis for this disease.

Pelvic Castleman disease: CT and MR appearance

The localized form of Castleman disease is rare and of unknown origin. Pelvic location of the disease is unusual. We report the CT and MR appearance of a case of pelvic Castleman disease presenting with characteristic calcifications and hypervascularity.