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Abstract
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<h5 class="section-title" id="d7772017e181">Background</h5>
<p id="d7772017e183">Large-scale studies comparing glomerular disease frequencies
across continents are
lacking.
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<h5 class="section-title" id="d7772017e186">Methods</h5>
<p id="d7772017e188">We surveyed 29 nephropathology laboratories in four continents
using a standardized
data collection form. We obtained recent consecutive kidney biopsy diagnosis frequencies
at each center and summary demographics for each diagnosis. This report focuses on
glomerular disease frequencies by region and race/ethnicity.
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<h5 class="section-title" id="d7772017e191">Results</h5>
<p id="d7772017e193">Among 42 603 glomerular disease diagnoses reported (median age
47 years, 52% male,
57% white), from a total of 60 340 diagnoses, glomerular disease subtype frequencies
differed considerably by continent. Diabetic glomerulosclerosis (GS; 19.1%) and focal
segmental glomerulosclerosis (FSGS; 19.1%) predominated in North America; lupus nephritis
(38.1%) and FSGS (15.8%) predominated in Latin America; IgA nephropathy (IgAN; 22.1%)
and FSGS (14.9%) predominated in Europe; and IgAN (39.5%) and lupus nephritis (16.8%)
predominated in Asia. After stratifying by race, diabetic GS (17.4% versus 4.3%, P < 0.001)
and FSGS (17.3% versus 11.8%, P < 0.001) were more, and lupus nephritis less (15.8%
versus 45.6%, P < 0.001), frequent among Latinos in North versus Latin America;
FSGS
was more (13.1% versus 7.1%, P < 0.001), and IgAN less (27.4% versus 40.5%, P < 0.001),
frequent among Asians in North America versus Asia; and FSGS (18.9% versus 13.5%,
P < 0.001) and diabetic GS (18.7% versus 6.5%, P < 0.001) were more, and IgAN
less
(14.4% versus 25.4%, P < 0.001), frequent among whites in North America versus
Europe.
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<h5 class="section-title" id="d7772017e196">Conclusions</h5>
<p id="d7772017e198">We determined that glomerular disease frequencies differed by
continent, even among
patients of similar race/ethnicity. Regional environmental and lifestyle factors,
and local biopsy policies, might influence glomerular disease epidemiology independently
of race/ethnicity.
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Little is known about the worldwide variation in incidence of primary glomerulonephritis (GN). The objective of this review was to critically appraise studies of incidence published in 1980-2010 so that an overall view of trends of these diseases can be found. This would provide important information for determining changes in rates and understanding variations between countries. All relevant papers found through searches of Medline, Embase and ScienceDirect were critically appraised and an assessment was made of the reliability of the reported incidence data. This review includes 40 studies of incidence of primary GN from Europe, North and South America, Canada, Australasia and the Middle East. Rates for the individual types of disease were found to be in adults, 0.2/100,000/year for membrano-proliferative GN, 0.2/100,000/year for mesangio-proliferative GN, 0.6/100,000/year for minimal change disease, 0.8/100,000/year for focal segmental glomerulosclerosis, 1.2/100,000/year for membranous nephropathy and 2.5/100,000/year for IgA nephropathy. Rates were lower in children at around 0.1/100,000/year with the exception of minimal change disease where incidence was reported to be 2.0/100,000/year in Caucasian children with higher rates in Arabian children (9.2/100,000/year) and Asian children (6.2-15.6/100,000/year). This study found that incidence rates of primary GN vary between 0.2/100,000/year and 2.5/100,000/year. The incidence of IgA nephropathy is at least 2.5/100,000/year in adults; this disease can exist subclinically and is therefore only detected by chance in some patients. In addition, referral policies for diagnostic biopsy vary between countries. This will affect the incidence rates found.
The prevalence of glomerular diseases differs according to geographic area, race, age and indications for a renal biopsy. This study was conducted to evaluate the distribution and changing patterns of renal diseases during the past 20 years in a large patient population in Korea. Patients aged 16 years or older who underwent a renal biopsy at Severance Hospital in the Yonsei University Health System from 1987 to 2006 were enrolled. All medical records were reviewed retrospectively. In total, 1818 patients (M:F = 1.02:1) were reviewed. Glomerulonephritis (GN) comprised 85.9% of the total biopsied cases. The most common primary GN was IgA nephropathy (IgAN) (28.3%), which was followed by minimal change disease (MCD) (15.5%), membranous nephropathy (MN) (12.3%), focal segmental glomerulosclerosis (FSGS) (5.6%) and membranoproliferative GN (MPGN) (4.0%). The most common secondary GN was lupus nephritis (8.7%). The most common idiopathic nephrotic syndrome was MCD (38.5%), which was followed by MN and IgAN. Among 128 (7.4%) patients who were HBsAg-positive, MN (30.5%) and MPGN (21.1%) were the most common GN. When the incidence rates between 1987-91 and 2002-06 were compared, IgAN increased from 25.6 to 34.5%, while MCD (from 23.2 to 7.0%) and MPGN (from 6.7 to 1.7%) decreased significantly (P < 0.01). IgAN was the most common primary GN, and MCD was the most common cause of nephrotic syndrome. In the 5-year quartile comparison, the relative frequency of IgAN increased, while the relative frequency of MCD and MPGN decreased significantly during the past 20 years.
Mapping by admixture linkage disequilibrium (LD) detected strong association between nonmuscle myosin heavy chain 9 gene (MYH9) variants on chromosome 22 and nondiabetic nephropathy in African Americans. MYH9-related variants were posited to be the probable, but not necessarily the definitive, causal variants as a result of impressive statistical evidence of association, renal expression, and a role in autosomal dominant MYH9 disorders characterized by progressive glomerulosclerosis (Epstein and Fechtner syndromes). Dense mapping within MYH9 revealed striking LD patterns and racial variation in risk allele frequencies, suggesting population genetic factors such as selection may be operative in this region. Genovese and colleagues examined large chromosomal regions adjacent to MYH9 using genome-wide association methods and non-HapMap single nucleotide polymorphisms identified in Yoruba from the 1000 Genomes project. Statistically stronger associations were detected between two independent sequence variants in the Apolipoprotein L1 gene (APOL1) and nondiabetic nephropathy in African Americans, with odds ratios of 10.5 in idiopathic FSGS and 7.3 in hypertension-attributed ESRD. These kidney disease risk variants likely rose to high frequency in Africa because they confer resistance to trypanosomal infection and protect from African sleeping sickness. Risk variants in MYH9 and APOL1 are in strong LD, and the genetic risk that was previously attributed to MYH9 may reside, in part or in whole, in APOL1, although more complex models of risk cannot be excluded. This association likely explains racial disparities in nondiabetic nephropathy as a result of the high prevalence of risk alleles in individuals of African ancestry.
[1
]Division of Nephrology, Stanford University School of Medicine, Palo Alto, CA, USA
[2
]Division of Nephrology and Hypertension, Department of Medicine and the Kidney Center,
University of North Carolina School of Medicine, Chapel Hill, NC, USA
[3
]Division of Nephropathology, Department of Pathology and Laboratory Medicine, University
of North Carolina School of Medicine, Chapel Hill, NC, USA
[4
]Fondazione Ricerca Molinette, Regina Margherita Hospital, Turin, Italy
[5
]Department of Pathology, Microbiology and Immunology, Division of Renal Pathology,
Vanderbilt University Medical Center, Nashville, TN, USA
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