- Email: [email protected]
Medullary cystic kidney disease type 1 in a large Native-American kindred
Medullary Cystic Kidney Disease Type 1 in a Large NativeAmerican Kindred Raymond L. Kiser, MD, Matthias T.F. Wolf, MD, Jeffrey L. Martin, MD, Isabella Zalewski, Massimo Attanasio, MD, Friedhelm Hildebrandt, MD and Philip Klemmer, MD ● Background: Autosomal dominant medullary cystic kidney disease type 1 (MCKD1; Mendelian Inheritance in Man 174000) is a hereditary tubulointerstitial renal disease. For MCKD1, a locus on chromosome 1q21 is published. Although there are characteristic biopsy and imaging findings for MCKD, clinical diagnosis of this disorder is still very difficult because unique phenotypic features are not always present in individual cases. Methods: In a large Native-American kindred with apparent autosomal dominant nephropathy, clinical findings in more than 50 individuals were collected and evaluated. Haplotype analysis for 34 individuals was performed. Results: We report the difficulties establishing the diagnosis of MCKD in a large Native-American kindred solely by means of clinical criteria. This kindred shows a wider range of age of disease onset than previously reported. Gout and hypertension were common, but no patient reported symptoms of salt wasting. By means of haplotype analysis linkage was shown to the MCKD1 locus (logarithm of the odds score, 3.34). Conclusion: Establishing a diagnosis of MCKD solely on clinical findings is difficult because signs and symptoms may be subtle, renal cysts may be absent in more than 50% of affected individuals, and renal histological abnormalities are nonspecific. In patients presenting with renal insufficiency from apparent interstitial disease, a thorough family history and genetic linkage studies are required to establish a diagnosis of MCKD. We suspect MCKD is underdiagnosed and the true incidence of MCKD1 in the general population may be underestimated. No further living-related transplantation should be performed until genetic testing can exclude potentially affected donors. Am J Kidney Dis 44:611-617. © 2004 by the National Kidney Foundation, Inc. INDEX WORDS: Medullary cystic kidney disease (MCKD); transplantation; haplotype analysis.
M
EDULLARY CYSTIC kidney disease (MCKD; Mendelian Inheritance in Man 174000) is a progressive chronic tubulointerstitial disorder with autosomal dominant inheritance.1 It shares many features with autosomal recessive juvenile nephronophthisis, and together, they comprise the nephronophthisisMCKD complex.2 MCKD recently has been linked to 2 loci, MCKD1 on chromosome 1q213 and MCKD2 on chromosome 16p23.4 In contrast to MCKD1, in patients with MCKD2, a more severe phenotype concerning hyperuricemia and gout has been described. Moreover, in patients with MCKD2, an earlier median age of onset has been reported (age of onset in MCKD2, 32 years compared with 62 years in MCKD1).4 Otherwise, these 2 diseases are clinically indistinguishable. Recently, Hart et al5 published the uromodulin gene, which encodes Tamm-Horsfall protein, as the responsible gene for MCKD2. Despite these advances in the pathogenesis of MCKD2, the gene for MCKD1 has not yet been isolated. Differentiation from other inherited progressive renal disorders relies on clinical presentation, renal histological characteristics, and radiographic imaging. However, these criteria are neither sensitive nor specific.6 The absence of a definitive test causes diagnostic confusion, leads
to incorrect categorization and underreporting, and raises dilemmas with regard to living related transplantation. We present a large family of Native Americans from North Carolina with previously undiagnosed MCKD (Fig 1). Despite having collectively consulted more than 10 nephrologists, the diagnosis was not suspected until the evening before a planned living-related transplantation (from daughter [VI:1] to father [V:5]; Fig 2). Radiographic evaluation of the daughter showed no renal cysts on ultrasound or computed tomographic scan. A percutaneous needle renal biopsy specimen showed mild tubular atrophy, thicken-
From the Division of Nephrology and Hypertension, University of North Carolina, Chapel Hill, NC; and Department of Pediatrics and Human Genetics, University of Michigan, Ann Arbor, MI. Received March 4, 2004; accepted in revised form June 17, 2004. R.L.K. and M.T.F.W. contributed equally to this article. Address reprint requests to Friedhelm Hildebrandt, MD, Department of Pediatrics and Communicable Diseases, University of Michigan, 8220C MSRB III, 1150 West Medical Center Dr, Ann Arbor, MI 48109-0646. E-mail: fhilde@ umich.edu © 2004 by the National Kidney Foundation, Inc. 0272-6386/04/4404-0005$30.00/0 doi:10.1053/j.ajkd.2004.06.027
American Journal of Kidney Diseases, Vol 44, No 4 (October), 2004: pp 611-617
611
612
KISER ET AL
Fig 1. Pedigree of the Native-American kindred with MCKD showing the autosomal dominant segregation during 4 generations. Fifty individuals from this kindred were available for this study. Circles, females; squares, males; filled symbols, 18 individuals affected by MCKD1; crosshatches, deceased individuals; Roman numerals, generations.
ing of the tubular basement membrane, and 20% globally sclerosed glomeruli. No specific diagnosis could be made. Given these abnormalities, the transplantation was cancelled. To further delineate the cause of this disease, we performed a history and physical examinations, reviewed medical records, and obtained blood for genetic analysis on 50 family members. METHODS
Patient Recruitment Approval for the evaluation of an inherited kidney disease was obtained from the institutional review board. An informational meeting was conducted with family members who had been seen within our group. Fifty individuals of this large kindred were available for additional evaluation, including all except 1 of the known living affected family members. We performed a history and physical examination, obtained prior medical records, and collected blood for genetic analysis for each of these family members. We obtained clinical information on deceased affected individuals from family members and reviewed their medical records after obtaining consent from the closest living relatives.
Linkage Analysis Blood samples and clinical data for a large multigeneration family with autosomal dominant nephropathy were obtained after informed consent was given by patients and unaffected relatives. Fifty blood samples were collected (11 samples, affected individuals; 39 samples, unaffected relatives or partners), and DNA was extracted for molecular analysis. Genomic DNA was isolated from blood samples by using standard methods.7 Haplotype analysis for linkage was performed in 34 individuals (11 affected and 23 unaffected relatives) by using 9 consecutive polymorphic microsatellite markers that span the critical MCKD1 region in the following order: cen-D1S305, D1S1153, D1S29H23c*, D1S303, D1S1595/S2140, D1S243J18b*, D1S243J18c*, D1S336K24a*, D1S2624-tel. Marked with asterisks are 4 novel polymorphic markers that were created by searching for microsatellite markers by using a list of dinucleotide, trinucleotide, and tetranucleotide repeats in a basic local alignment search tool (BLAST) search8 against sequence of the minimal contigs of the critical MCKD1 region.8-10 Fluorescently labeled polymerase chain reaction products were detected by using a Genetic Analyzer 3100 (Applied Biosystems, Foster City, CA) and analyzed by using Genotyper software (Applied Biosystems). Two-point logarithm of the odds (LOD) score calculations were performed by means of the Linkage program package,11 using an autosomal dominant model with 100% penetrance, a gene frequency for
MCKD TYPE 1 IN A LARGE NATIVE-AMERICAN KINDRED
613
Fig 2. Results of haplotype analysis of 9 markers at the MCKD1 locus in 12 individuals from the Native-American MCKD1 kindred. Circles, females; squares, males; filled symbols, affected individuals; differently shaded bars, haplotypes. Paternal haplotypes are drawn to the left; maternal haplotypes, to the right. Marker positions are indicated with left individuals. All affected individuals participating in the study and their parents (in most cases deceased) are shown with their haplotypes at chromosome 1q21. Using an affecteds-only approach, the white haplotype showed complete cosegregation with the phenotype in all 12 living affected individuals of this kindred. Data for unaffected individuals who are potential gene carriers have been deleted to preserve confidentiality.
614
KISER ET AL Table 1. Presenting Symptoms in the 18 Affected Family Members
Elevated Serum Creatinine*
Uremia
Fatigue
Hypertension
Donor Evaluation
8 (44)
5 (28)
3 (17)
1 (5)
1 (5)
NOTE. Values are expressed as number (%).
*Found on routine laboratory tests. MCKD 1 of 0.0001. Because of the reduced penetrance described in MCKD1, calculations were performed on the basis of an “affecteds-only” strategy.
RESULTS
The family consists of more than 100 living members, 50 of whom were available for this study (Fig 1). Clinical information was obtained on the 18 known affected individuals, 12 of whom were living. Of these, 5 individuals were being followed up for chronic renal insufficiency, 4 individuals were on hemodialysis therapy, 3 individuals had functioning transplants, and the potential donor presented here (VI:1; Fig 2) had normal laboratory results. Two transplants were living-related donations from siblings. Both donors were doing well without signs of renal disease. Clinical Presentation Age of onset of renal insufficiency (defined as serum creatinine level ⬎1.4 mg/dL [⬎124 mol/L] in females or ⬎1.5 mg/dL [⬎133 mol/L] in males) ranged from 34 to 65 years (median, 41 years). Age of development of endstage renal disease (defined as the need for renal replacement therapy) ranged from 35 to 66 years (median, 47 years). The first 5 affected patients, all diagnosed before 1980, presented with florid uremia. Of the remaining affected patients, the most common presentation was an elevated serum creatinine level found on routine laboratory tests in an otherwise asymptomatic patient (Table 1). No patient presented with polyuria, polydipsia, or urinary salt wasting. No patients had diabetes. No abnormalities were found on physical examinations. Other medical problems at the time of diagnosis included gout (61%), hypertension (55%), and anemia (39%). The diagnosis of gout was made from a clinical history of monoarthritis, most commonly affecting the great toe. Hypertension is defined as blood pressure greater than
140/90 mm Hg. Anemia is defined as a hemoglobin level less than 14 g/dL (⬍140 g/L) in males and less than 12 g/dL (⬍120 g/L) in females.12 Urinary Findings Urinalysis results were obtained for 11 affected patients. All had zero or trace hematuria. Nine patients had zero to trace proteinuria. The 2 patients with significant proteinuria on urinalysis had 24-hour collections completed. Patient V:5 had protein excretion of 2,050 mg/d, and patient V:33 had protein excretion of 570 mg/d. Radiographic Assessment Nine affected patients had renal ultrasounds performed. Four ultrasounds showed cysts. One patient had small bilateral cysts at the corticomedullary junction, whereas 3 ultrasounds were described to be consistent with acquired cystic disease. Of the 5 remaining ultrasounds, 3 showed mild increased echogenicity and 2 were read as normal. One patient (V:29) also underwent abdominal magnetic resonance imaging. No renal cysts were seen at that time, which was approximately 6 months after diagnosis. A follow-up ultrasound on the same patient 10 years later still showed no cysts. Histopathologic Examination Renal biopsies were performed on 4 affected patients (Table 2). Common findings were glomerular sclerosis, tubular atrophy, interstitial fibrosis, chronic interstitial inflammation, and arterionephrosclerosis. None was described initially as consistent with MCKD, and on retrospective review by our nephropathologist, only 1 specimen was reported to be diagnostic for MCKD. Linkage Analysis We used an affecteds-only approach for definition of the affected status of MCKD. Specifically, if diagnostic data supported MCKD, af-
MCKD TYPE 1 IN A LARGE NATIVE-AMERICAN KINDRED
615
Table 2. Renal Biopsy Results in 4 of the 12 Living Affected Individuals Patient
Biopsy Results
IV:12
Moderate patchy interstitial fibrosis, tubular atrophy, chronic inflammation, arterionephrosclerosis, tubules in nonfibrotic areas did not show any specific changes Inadequate biopsy specimen with no glomeruli, but normal-appearing interstitium Fifty percent of glomeruli were globally sclerotic; tubular atrophy, interstitial fibrosis, marked arterionephrosclerosis Twenty percent globally sclerosed glomeruli, tubular atrophy with thickened basement membranes, interstitial fibrosis with a mixed inflammatory infiltrate, mild arterionephrosclerosis
V:29 V:36 VI:1
fected status was assumed. If there were no data showing the presence of MCKD, disease status was determined as unknown because there is age-related penetrance in MCKD. On this basis, there was full cosegregation of a haplotype of marker alleles and affected status for MCKD. Two-point LOD scores were positive at MCKD1 and showed significant linkage (Table 3). The maximum 2-point LOD score was 3.34 for D1S303 (Table 2). Critical meiotic recombinants place MCKD1 in the interval between D1S30510 and D1S2125.3
hypertension, glomerulonephritis, or unknown. Nevertheless, we successfully diagnosed MCKD in this kindred, proving clinical diagnosis by significant linkage as a result of haplotype analysis. Incorrect diagnosis of MCKD results from nonspecific symptoms, late presentation, and lack of accurate diagnostic tests. In the urine of some patients with MCKD2, reduced fractional excretion of uric acid (FEurate) was described, which may help establish the diagnosis in patients with MCKD2.5,14 Nevertheless, FEurate is related to renal function and thus may complicate its diagnostic value. Moreover, low FEurate also was published in several unaffected and control patients; therefore, urinary FEurate has to be analyzed very carefully. For patients with MCKD1, Stavrou et al15 could not find a difference in FEurate values between MCKD1 gene mutation carriers and noncarriers. An additional tool for the diagnosis of MCKD2 may be analysis of urinary Tamm-Horsfall protein excretion. In a subset of patients with uromodulin gene mutations (6 and 2 patients, respectively), reduced urinary Tamm-Horsfall protein excretion was published.16,17 Additional studies are necessary
DISCUSSION
MCKD is an infrequently reported cause of end-stage renal disease in the United States. The prevalence in 1999 from the United States Renal Data System database was only 256 total cases, with an annual incidence ranging from 34 to 56 new cases per year during the last 5 years.13 Underreporting because of incorrect diagnosis certainly contributes to this low prevalence. Eleven members of this family currently are or previously were on dialysis therapy. None of them carried the diagnosis of MCKD, and the cause of their renal failure was recorded as
Table 3. Two-Point LOD Scores at the MCKD1 Locus in the Native-American MCKD Kindred 2-Point LOD Score at ⫽
D1S305 D1D1153 D1S29H23c D1S303 D1S1595 D1S243J18b D1S243J18c D1S336K24a D1S2624
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
2.94 3.12 1.34 3.34 1.63 0.66 1.57 2.5 1.66
2.67 2.84 1.21 3.06 1.48 0.6 1.42 2.23 1.47
2.39 2.55 1.07 2.76 1.32 0.52 1.26 1.96 1.28
2.1 2.24 0.92 2.45 1.16 0.45 1.1 1.69 1.09
1.8 1.92 0.75 2.12 0.99 0.36 0.92 1.41 0.89
1.48 1.59 0.59 1.77 0.81 0.28 0.74 1.13 0.7
1.15 1.24 0.42 1.4 0.63 0.2 0.56 0.86 0.51
0.82 0.89 0.26 1.02 0.46 0.12 0.37 0.61 0.33
0.5 0.54 0.12 0.63 0.29 0.06 0.21 0.38 0.17
616
to establish the diagnostic value of urinary TammHorsfall protein excretion in the diagnosis of MCKD2. The most common presentation in this family was abnormal laboratory data obtained for other reasons. Early generations presented with uremia, but this most likely was caused by poor health care access. Hypertension, although frequent, usually was mild. Gout often was present in affected patients, but preceded the diagnosis of MCKD by many years in at least 2 individuals. No patient presented with pulmonary or lower-extremity edema or salt wasting. Lack of severe symptoms early in this disease leads to late presentation to physicians and a low rate of renal survival after the initial diagnosis. Even after presentation, diagnosis remains difficult. We define renal insufficiency as a serum creatinine level greater than 1.4 mg/dL (⬎124 mol/L) in females and greater than 1.5 mg/dL (⬎133 mol/L) in males. This definition could exclude some patients with early renal impairment because serum creatinine is affected by sex, age, body weight, and renal function. Nevertheless, we use serum creatinine level to avoid falsepositive assignment of nonaffected patients, who may be indistinguishable from patients with early renal impairment. Urinalysis findings often are unremarkable. Lack of active urinary sediment or heavy proteinuria subsequently leads to infrequent renal biopsies. Even when renal biopsies are performed, the diagnosis may remain elusive. The classic pathological triad for MCKD is tubular basement membrane disintegration with irregular thickening, interstitial round-cell infiltration with marked fibrosis, and tubular atrophy with possible cyst formation at the corticomedullary junction.2 Not all these conditions may be present in a single patient, and findings may not be sufficient to establish a diagnosis. Given the name of this disease, radiographic findings would seem to be helpful. Medullary cysts have been reported to be present in up to 40.3% of patients.15 This is similar to the prevalence of cysts in the kindred described here (44%). In 1 affected individual with end-stage renal disease, even magnetic resonance imaging failed to identify cysts. These findings correspond to clinical symptoms described in an Iraqi Jewish kindred. This published kindred showed only renal failure and hypertension, but no renal cysts on ultra-
KISER ET AL
sound, no gout, no hyperuricemia, and no salt wasting, which emphasizes the broad spectrum of symptoms and difficulties in the diagnosis of MCKD1.18 The resulting dilemma is that without a family history suggestive of autosomal dominance, MCKD is a very difficult diagnosis to make. This diagnostic dilemma then creates additional issues with regard to living related donor transplantation. Polycystic kidney disease, the most common inherited cause of progressive renal disorders, has the benefit of both radiographic and genetic testing to exclude affected asymptomatic donors.19 Based on our experience, not even normal magnetic resonance imaging results of the kidneys can exclude MCKD. Commercial testing now is available for MCKD2, but the gene for MCKD1 remains elusive.5 Testing for MCKD2 should be performed in all cases in which MCKD1 is suspected because the diseases have remarkable overlap. Unfortunately, age cannot be used as a criterion for potential donors. Renal disease has occurred as young as 24 years and as old as 80 years in patients with MCKD.15,18 Given this ambiguity regarding diagnosis, we are excluding all living relatives as potential donors for patients with end-stage renal disease caused by MCKD. Hopefully, in the near future, identification of the MCKD1 gene will enable clinicians to make early and accurate diagnosis of this heritable and probably underreported renal disease. Recently, a critical interval of 650 kb for the MCKD1 locus was defined.20 This still is relatively large and may contain more than 1 responsible gene. Therefore, more than 1 gene within the critical MCKD1 region may be involved in MCKD1 pathogenesis. REFERENCES 1. Gardner KDJ: Evolution of clinical signs in adultonset cystic disease of the renal medulla. Ann Intern Med 74:47-54, 1971 2. Waldherr R, Lennert T, Weber HP, Fodisch HJ, Scharer K: The nephronophthisis complex: A clinicopathologic study in children. Virchows Arch 394:235-254, 1982 3. Christodoulou K, Tsingis M, Stavrou C, et al: Chromosome 1 localization of a gene for autosomal dominant medullary cystic kidney disease. Hum Mol Genet 7:905911, 1998 4. Scolari F, Puzzer D, Amoroso A, et al: Identification of a new locus for medullary cystic disease, on chromosome 16p12. Am J Hum Genet 64:1655-1660, 1999
MCKD TYPE 1 IN A LARGE NATIVE-AMERICAN KINDRED
5. Hart TC, Gorry MC, Hart PS, et al: Mutations of the UMOD gene are responsible for medullary cystic kidney disease 2 and familial juvenile hyperuricaemic nephropathy. J Med Genet 39:882-892, 2002 6. Hildebrandt F, Otto E: Molecular genetics of nephronophthisis and medullary cystic kidney disease. J Am Soc Nephrol 11:1753-1761, 2000 7. Sambrook J, Fritsch EF, Maniatis T: Molecular Cloning: A Laboratory Manual (ed 2). Cold Spring Harbor, NY, Cold Spring Harbor Laboratory, 1989, pp 9.17-9.19 8. The National Center for Biotechnology Information: BLAST. Available at: http://www.ncbi.nlm.nih.gov/BLAST/. Accessed: October 13, 2002 9. A joint project between the European Bioinformatics Institute and the Sanger Institute. Available at: http:// www.ensembl.org. Accessed: October 13, 2002 10. Fuchshuber A, Kroiss S, Karle S, et al: Refinement of the gene locus for autosomal dominant medullary cystic kidney disease type 1 (MCKD1) and construction of a physical and partial transcriptional map of the region. Genomics 72:278-284, 2001 11. Lathrop GM, Lalouel JM: Easy calculations of LOD scores and genetic risks on small computers. Am J Hum Genet 36:460-465, 1984 12. Fairbanks VF, Tefferi A: Normal ranges for packed cell volume and hemoglobin concentration in adults. Eur J Haematol 65:285-296, 2000
617
13. US Renal Data System: Data request. Available at: http://www.usrds.org/request.asp. Accessed: October 11, 2002 14. Bleyer AJ, Woodard AS, Shihabi Z, et al: Clinical characterization of a family with a mutation in the uromodulin (Tamm-Horsfall glycoprotein) gene. Kidney Int 64:3642, 2003 15. Stavrou C, Koptides M, Tombazos C, et al: Autosomal dominant medullary cystic kidney type 1: Clinical and molecular findings in six large Cypriot families. Kidney Int 62:1385-1394, 2002 16. Dahan K, Devuyst O, Smaers M, et al: A cluster of mutations in the UMOD gene causes familial juvenile hyperuricemic nephropathy with abnormal expression of uromodulin. J Am Soc Nephrol 14:2883-2893, 2003 17. Rampoldi L, Caridi G, Santon D, et al: Allelism of MCKD, FJHN and GCKD caused by impairment of uromodulin export dynamics. Hum Mol Genet 12:3369-3384, 2003 18. Parvari R, Shnaider A, Basok A, et al: Clinical and genetic characterization of an autosomal dominant nephropathy. Am J Med Genet 99:204-209, 2001 19. Parfrey PS, Bear JC, Morgan J, et al: The diagnosis and prognosis of autosomal dominant polycystic kidney disease. N Engl J Med 323:1085-1090, 1990 20. Wolf MTF, Karle SM, Schwarz S, et al: Refinement of the critical region for MCKD1 by detection of transcontinental haplotype sharing. Kidney Int 64:788-792, 2003
M
EDULLARY CYSTIC kidney disease (MCKD; Mendelian Inheritance in Man 174000) is a progressive chronic tubulointerstitial disorder with autosomal dominant inheritance.1 It shares many features with autosomal recessive juvenile nephronophthisis, and together, they comprise the nephronophthisisMCKD complex.2 MCKD recently has been linked to 2 loci, MCKD1 on chromosome 1q213 and MCKD2 on chromosome 16p23.4 In contrast to MCKD1, in patients with MCKD2, a more severe phenotype concerning hyperuricemia and gout has been described. Moreover, in patients with MCKD2, an earlier median age of onset has been reported (age of onset in MCKD2, 32 years compared with 62 years in MCKD1).4 Otherwise, these 2 diseases are clinically indistinguishable. Recently, Hart et al5 published the uromodulin gene, which encodes Tamm-Horsfall protein, as the responsible gene for MCKD2. Despite these advances in the pathogenesis of MCKD2, the gene for MCKD1 has not yet been isolated. Differentiation from other inherited progressive renal disorders relies on clinical presentation, renal histological characteristics, and radiographic imaging. However, these criteria are neither sensitive nor specific.6 The absence of a definitive test causes diagnostic confusion, leads
to incorrect categorization and underreporting, and raises dilemmas with regard to living related transplantation. We present a large family of Native Americans from North Carolina with previously undiagnosed MCKD (Fig 1). Despite having collectively consulted more than 10 nephrologists, the diagnosis was not suspected until the evening before a planned living-related transplantation (from daughter [VI:1] to father [V:5]; Fig 2). Radiographic evaluation of the daughter showed no renal cysts on ultrasound or computed tomographic scan. A percutaneous needle renal biopsy specimen showed mild tubular atrophy, thicken-
From the Division of Nephrology and Hypertension, University of North Carolina, Chapel Hill, NC; and Department of Pediatrics and Human Genetics, University of Michigan, Ann Arbor, MI. Received March 4, 2004; accepted in revised form June 17, 2004. R.L.K. and M.T.F.W. contributed equally to this article. Address reprint requests to Friedhelm Hildebrandt, MD, Department of Pediatrics and Communicable Diseases, University of Michigan, 8220C MSRB III, 1150 West Medical Center Dr, Ann Arbor, MI 48109-0646. E-mail: fhilde@ umich.edu © 2004 by the National Kidney Foundation, Inc. 0272-6386/04/4404-0005$30.00/0 doi:10.1053/j.ajkd.2004.06.027
American Journal of Kidney Diseases, Vol 44, No 4 (October), 2004: pp 611-617
611
612
KISER ET AL
Fig 1. Pedigree of the Native-American kindred with MCKD showing the autosomal dominant segregation during 4 generations. Fifty individuals from this kindred were available for this study. Circles, females; squares, males; filled symbols, 18 individuals affected by MCKD1; crosshatches, deceased individuals; Roman numerals, generations.
ing of the tubular basement membrane, and 20% globally sclerosed glomeruli. No specific diagnosis could be made. Given these abnormalities, the transplantation was cancelled. To further delineate the cause of this disease, we performed a history and physical examinations, reviewed medical records, and obtained blood for genetic analysis on 50 family members. METHODS
Patient Recruitment Approval for the evaluation of an inherited kidney disease was obtained from the institutional review board. An informational meeting was conducted with family members who had been seen within our group. Fifty individuals of this large kindred were available for additional evaluation, including all except 1 of the known living affected family members. We performed a history and physical examination, obtained prior medical records, and collected blood for genetic analysis for each of these family members. We obtained clinical information on deceased affected individuals from family members and reviewed their medical records after obtaining consent from the closest living relatives.
Linkage Analysis Blood samples and clinical data for a large multigeneration family with autosomal dominant nephropathy were obtained after informed consent was given by patients and unaffected relatives. Fifty blood samples were collected (11 samples, affected individuals; 39 samples, unaffected relatives or partners), and DNA was extracted for molecular analysis. Genomic DNA was isolated from blood samples by using standard methods.7 Haplotype analysis for linkage was performed in 34 individuals (11 affected and 23 unaffected relatives) by using 9 consecutive polymorphic microsatellite markers that span the critical MCKD1 region in the following order: cen-D1S305, D1S1153, D1S29H23c*, D1S303, D1S1595/S2140, D1S243J18b*, D1S243J18c*, D1S336K24a*, D1S2624-tel. Marked with asterisks are 4 novel polymorphic markers that were created by searching for microsatellite markers by using a list of dinucleotide, trinucleotide, and tetranucleotide repeats in a basic local alignment search tool (BLAST) search8 against sequence of the minimal contigs of the critical MCKD1 region.8-10 Fluorescently labeled polymerase chain reaction products were detected by using a Genetic Analyzer 3100 (Applied Biosystems, Foster City, CA) and analyzed by using Genotyper software (Applied Biosystems). Two-point logarithm of the odds (LOD) score calculations were performed by means of the Linkage program package,11 using an autosomal dominant model with 100% penetrance, a gene frequency for
MCKD TYPE 1 IN A LARGE NATIVE-AMERICAN KINDRED
613
Fig 2. Results of haplotype analysis of 9 markers at the MCKD1 locus in 12 individuals from the Native-American MCKD1 kindred. Circles, females; squares, males; filled symbols, affected individuals; differently shaded bars, haplotypes. Paternal haplotypes are drawn to the left; maternal haplotypes, to the right. Marker positions are indicated with left individuals. All affected individuals participating in the study and their parents (in most cases deceased) are shown with their haplotypes at chromosome 1q21. Using an affecteds-only approach, the white haplotype showed complete cosegregation with the phenotype in all 12 living affected individuals of this kindred. Data for unaffected individuals who are potential gene carriers have been deleted to preserve confidentiality.
614
KISER ET AL Table 1. Presenting Symptoms in the 18 Affected Family Members
Elevated Serum Creatinine*
Uremia
Fatigue
Hypertension
Donor Evaluation
8 (44)
5 (28)
3 (17)
1 (5)
1 (5)
NOTE. Values are expressed as number (%).
*Found on routine laboratory tests. MCKD 1 of 0.0001. Because of the reduced penetrance described in MCKD1, calculations were performed on the basis of an “affecteds-only” strategy.
RESULTS
The family consists of more than 100 living members, 50 of whom were available for this study (Fig 1). Clinical information was obtained on the 18 known affected individuals, 12 of whom were living. Of these, 5 individuals were being followed up for chronic renal insufficiency, 4 individuals were on hemodialysis therapy, 3 individuals had functioning transplants, and the potential donor presented here (VI:1; Fig 2) had normal laboratory results. Two transplants were living-related donations from siblings. Both donors were doing well without signs of renal disease. Clinical Presentation Age of onset of renal insufficiency (defined as serum creatinine level ⬎1.4 mg/dL [⬎124 mol/L] in females or ⬎1.5 mg/dL [⬎133 mol/L] in males) ranged from 34 to 65 years (median, 41 years). Age of development of endstage renal disease (defined as the need for renal replacement therapy) ranged from 35 to 66 years (median, 47 years). The first 5 affected patients, all diagnosed before 1980, presented with florid uremia. Of the remaining affected patients, the most common presentation was an elevated serum creatinine level found on routine laboratory tests in an otherwise asymptomatic patient (Table 1). No patient presented with polyuria, polydipsia, or urinary salt wasting. No patients had diabetes. No abnormalities were found on physical examinations. Other medical problems at the time of diagnosis included gout (61%), hypertension (55%), and anemia (39%). The diagnosis of gout was made from a clinical history of monoarthritis, most commonly affecting the great toe. Hypertension is defined as blood pressure greater than
140/90 mm Hg. Anemia is defined as a hemoglobin level less than 14 g/dL (⬍140 g/L) in males and less than 12 g/dL (⬍120 g/L) in females.12 Urinary Findings Urinalysis results were obtained for 11 affected patients. All had zero or trace hematuria. Nine patients had zero to trace proteinuria. The 2 patients with significant proteinuria on urinalysis had 24-hour collections completed. Patient V:5 had protein excretion of 2,050 mg/d, and patient V:33 had protein excretion of 570 mg/d. Radiographic Assessment Nine affected patients had renal ultrasounds performed. Four ultrasounds showed cysts. One patient had small bilateral cysts at the corticomedullary junction, whereas 3 ultrasounds were described to be consistent with acquired cystic disease. Of the 5 remaining ultrasounds, 3 showed mild increased echogenicity and 2 were read as normal. One patient (V:29) also underwent abdominal magnetic resonance imaging. No renal cysts were seen at that time, which was approximately 6 months after diagnosis. A follow-up ultrasound on the same patient 10 years later still showed no cysts. Histopathologic Examination Renal biopsies were performed on 4 affected patients (Table 2). Common findings were glomerular sclerosis, tubular atrophy, interstitial fibrosis, chronic interstitial inflammation, and arterionephrosclerosis. None was described initially as consistent with MCKD, and on retrospective review by our nephropathologist, only 1 specimen was reported to be diagnostic for MCKD. Linkage Analysis We used an affecteds-only approach for definition of the affected status of MCKD. Specifically, if diagnostic data supported MCKD, af-
MCKD TYPE 1 IN A LARGE NATIVE-AMERICAN KINDRED
615
Table 2. Renal Biopsy Results in 4 of the 12 Living Affected Individuals Patient
Biopsy Results
IV:12
Moderate patchy interstitial fibrosis, tubular atrophy, chronic inflammation, arterionephrosclerosis, tubules in nonfibrotic areas did not show any specific changes Inadequate biopsy specimen with no glomeruli, but normal-appearing interstitium Fifty percent of glomeruli were globally sclerotic; tubular atrophy, interstitial fibrosis, marked arterionephrosclerosis Twenty percent globally sclerosed glomeruli, tubular atrophy with thickened basement membranes, interstitial fibrosis with a mixed inflammatory infiltrate, mild arterionephrosclerosis
V:29 V:36 VI:1
fected status was assumed. If there were no data showing the presence of MCKD, disease status was determined as unknown because there is age-related penetrance in MCKD. On this basis, there was full cosegregation of a haplotype of marker alleles and affected status for MCKD. Two-point LOD scores were positive at MCKD1 and showed significant linkage (Table 3). The maximum 2-point LOD score was 3.34 for D1S303 (Table 2). Critical meiotic recombinants place MCKD1 in the interval between D1S30510 and D1S2125.3
hypertension, glomerulonephritis, or unknown. Nevertheless, we successfully diagnosed MCKD in this kindred, proving clinical diagnosis by significant linkage as a result of haplotype analysis. Incorrect diagnosis of MCKD results from nonspecific symptoms, late presentation, and lack of accurate diagnostic tests. In the urine of some patients with MCKD2, reduced fractional excretion of uric acid (FEurate) was described, which may help establish the diagnosis in patients with MCKD2.5,14 Nevertheless, FEurate is related to renal function and thus may complicate its diagnostic value. Moreover, low FEurate also was published in several unaffected and control patients; therefore, urinary FEurate has to be analyzed very carefully. For patients with MCKD1, Stavrou et al15 could not find a difference in FEurate values between MCKD1 gene mutation carriers and noncarriers. An additional tool for the diagnosis of MCKD2 may be analysis of urinary Tamm-Horsfall protein excretion. In a subset of patients with uromodulin gene mutations (6 and 2 patients, respectively), reduced urinary Tamm-Horsfall protein excretion was published.16,17 Additional studies are necessary
DISCUSSION
MCKD is an infrequently reported cause of end-stage renal disease in the United States. The prevalence in 1999 from the United States Renal Data System database was only 256 total cases, with an annual incidence ranging from 34 to 56 new cases per year during the last 5 years.13 Underreporting because of incorrect diagnosis certainly contributes to this low prevalence. Eleven members of this family currently are or previously were on dialysis therapy. None of them carried the diagnosis of MCKD, and the cause of their renal failure was recorded as
Table 3. Two-Point LOD Scores at the MCKD1 Locus in the Native-American MCKD Kindred 2-Point LOD Score at ⫽
D1S305 D1D1153 D1S29H23c D1S303 D1S1595 D1S243J18b D1S243J18c D1S336K24a D1S2624
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
2.94 3.12 1.34 3.34 1.63 0.66 1.57 2.5 1.66
2.67 2.84 1.21 3.06 1.48 0.6 1.42 2.23 1.47
2.39 2.55 1.07 2.76 1.32 0.52 1.26 1.96 1.28
2.1 2.24 0.92 2.45 1.16 0.45 1.1 1.69 1.09
1.8 1.92 0.75 2.12 0.99 0.36 0.92 1.41 0.89
1.48 1.59 0.59 1.77 0.81 0.28 0.74 1.13 0.7
1.15 1.24 0.42 1.4 0.63 0.2 0.56 0.86 0.51
0.82 0.89 0.26 1.02 0.46 0.12 0.37 0.61 0.33
0.5 0.54 0.12 0.63 0.29 0.06 0.21 0.38 0.17
616
to establish the diagnostic value of urinary TammHorsfall protein excretion in the diagnosis of MCKD2. The most common presentation in this family was abnormal laboratory data obtained for other reasons. Early generations presented with uremia, but this most likely was caused by poor health care access. Hypertension, although frequent, usually was mild. Gout often was present in affected patients, but preceded the diagnosis of MCKD by many years in at least 2 individuals. No patient presented with pulmonary or lower-extremity edema or salt wasting. Lack of severe symptoms early in this disease leads to late presentation to physicians and a low rate of renal survival after the initial diagnosis. Even after presentation, diagnosis remains difficult. We define renal insufficiency as a serum creatinine level greater than 1.4 mg/dL (⬎124 mol/L) in females and greater than 1.5 mg/dL (⬎133 mol/L) in males. This definition could exclude some patients with early renal impairment because serum creatinine is affected by sex, age, body weight, and renal function. Nevertheless, we use serum creatinine level to avoid falsepositive assignment of nonaffected patients, who may be indistinguishable from patients with early renal impairment. Urinalysis findings often are unremarkable. Lack of active urinary sediment or heavy proteinuria subsequently leads to infrequent renal biopsies. Even when renal biopsies are performed, the diagnosis may remain elusive. The classic pathological triad for MCKD is tubular basement membrane disintegration with irregular thickening, interstitial round-cell infiltration with marked fibrosis, and tubular atrophy with possible cyst formation at the corticomedullary junction.2 Not all these conditions may be present in a single patient, and findings may not be sufficient to establish a diagnosis. Given the name of this disease, radiographic findings would seem to be helpful. Medullary cysts have been reported to be present in up to 40.3% of patients.15 This is similar to the prevalence of cysts in the kindred described here (44%). In 1 affected individual with end-stage renal disease, even magnetic resonance imaging failed to identify cysts. These findings correspond to clinical symptoms described in an Iraqi Jewish kindred. This published kindred showed only renal failure and hypertension, but no renal cysts on ultra-
KISER ET AL
sound, no gout, no hyperuricemia, and no salt wasting, which emphasizes the broad spectrum of symptoms and difficulties in the diagnosis of MCKD1.18 The resulting dilemma is that without a family history suggestive of autosomal dominance, MCKD is a very difficult diagnosis to make. This diagnostic dilemma then creates additional issues with regard to living related donor transplantation. Polycystic kidney disease, the most common inherited cause of progressive renal disorders, has the benefit of both radiographic and genetic testing to exclude affected asymptomatic donors.19 Based on our experience, not even normal magnetic resonance imaging results of the kidneys can exclude MCKD. Commercial testing now is available for MCKD2, but the gene for MCKD1 remains elusive.5 Testing for MCKD2 should be performed in all cases in which MCKD1 is suspected because the diseases have remarkable overlap. Unfortunately, age cannot be used as a criterion for potential donors. Renal disease has occurred as young as 24 years and as old as 80 years in patients with MCKD.15,18 Given this ambiguity regarding diagnosis, we are excluding all living relatives as potential donors for patients with end-stage renal disease caused by MCKD. Hopefully, in the near future, identification of the MCKD1 gene will enable clinicians to make early and accurate diagnosis of this heritable and probably underreported renal disease. Recently, a critical interval of 650 kb for the MCKD1 locus was defined.20 This still is relatively large and may contain more than 1 responsible gene. Therefore, more than 1 gene within the critical MCKD1 region may be involved in MCKD1 pathogenesis. REFERENCES 1. Gardner KDJ: Evolution of clinical signs in adultonset cystic disease of the renal medulla. Ann Intern Med 74:47-54, 1971 2. Waldherr R, Lennert T, Weber HP, Fodisch HJ, Scharer K: The nephronophthisis complex: A clinicopathologic study in children. Virchows Arch 394:235-254, 1982 3. Christodoulou K, Tsingis M, Stavrou C, et al: Chromosome 1 localization of a gene for autosomal dominant medullary cystic kidney disease. Hum Mol Genet 7:905911, 1998 4. Scolari F, Puzzer D, Amoroso A, et al: Identification of a new locus for medullary cystic disease, on chromosome 16p12. Am J Hum Genet 64:1655-1660, 1999
MCKD TYPE 1 IN A LARGE NATIVE-AMERICAN KINDRED
5. Hart TC, Gorry MC, Hart PS, et al: Mutations of the UMOD gene are responsible for medullary cystic kidney disease 2 and familial juvenile hyperuricaemic nephropathy. J Med Genet 39:882-892, 2002 6. Hildebrandt F, Otto E: Molecular genetics of nephronophthisis and medullary cystic kidney disease. J Am Soc Nephrol 11:1753-1761, 2000 7. Sambrook J, Fritsch EF, Maniatis T: Molecular Cloning: A Laboratory Manual (ed 2). Cold Spring Harbor, NY, Cold Spring Harbor Laboratory, 1989, pp 9.17-9.19 8. The National Center for Biotechnology Information: BLAST. Available at: http://www.ncbi.nlm.nih.gov/BLAST/. Accessed: October 13, 2002 9. A joint project between the European Bioinformatics Institute and the Sanger Institute. Available at: http:// www.ensembl.org. Accessed: October 13, 2002 10. Fuchshuber A, Kroiss S, Karle S, et al: Refinement of the gene locus for autosomal dominant medullary cystic kidney disease type 1 (MCKD1) and construction of a physical and partial transcriptional map of the region. Genomics 72:278-284, 2001 11. Lathrop GM, Lalouel JM: Easy calculations of LOD scores and genetic risks on small computers. Am J Hum Genet 36:460-465, 1984 12. Fairbanks VF, Tefferi A: Normal ranges for packed cell volume and hemoglobin concentration in adults. Eur J Haematol 65:285-296, 2000
617
13. US Renal Data System: Data request. Available at: http://www.usrds.org/request.asp. Accessed: October 11, 2002 14. Bleyer AJ, Woodard AS, Shihabi Z, et al: Clinical characterization of a family with a mutation in the uromodulin (Tamm-Horsfall glycoprotein) gene. Kidney Int 64:3642, 2003 15. Stavrou C, Koptides M, Tombazos C, et al: Autosomal dominant medullary cystic kidney type 1: Clinical and molecular findings in six large Cypriot families. Kidney Int 62:1385-1394, 2002 16. Dahan K, Devuyst O, Smaers M, et al: A cluster of mutations in the UMOD gene causes familial juvenile hyperuricemic nephropathy with abnormal expression of uromodulin. J Am Soc Nephrol 14:2883-2893, 2003 17. Rampoldi L, Caridi G, Santon D, et al: Allelism of MCKD, FJHN and GCKD caused by impairment of uromodulin export dynamics. Hum Mol Genet 12:3369-3384, 2003 18. Parvari R, Shnaider A, Basok A, et al: Clinical and genetic characterization of an autosomal dominant nephropathy. Am J Med Genet 99:204-209, 2001 19. Parfrey PS, Bear JC, Morgan J, et al: The diagnosis and prognosis of autosomal dominant polycystic kidney disease. N Engl J Med 323:1085-1090, 1990 20. Wolf MTF, Karle SM, Schwarz S, et al: Refinement of the critical region for MCKD1 by detection of transcontinental haplotype sharing. Kidney Int 64:788-792, 2003