Q) I have heard about a gene that causes high blood pressure. Did I hear that right? Is testing for this gene available now?
African-Americans have a higher risk for chronic kidney disease (CKD), including end-stage renal disease (ESRD; defined as kidney failure requiring dialysis or transplant), than any other racial or ethnic group in the United States.1 Previously, this has been attributed to poorly controlled hypertension and diabetes, as well as socioeconomic factors such as limited access to health care.
Research now shows that autosomal recessive genetic variations on chromosome 22q, the gene that encodes apolipoprotein-1 (APOL1; an HDL protein), promote hypertension. This subsequently increases the risk for and progression of CKD in black patients (who have up to 29x higher risk than white patients without this genetic variation).2
The APOL1 gene has two alleles. Having at least one of them provides resistance to Trypanosoma brucei, the cause of “sleeping sickness” transmitted by the tsetse fly, but increases risk for CKD and ESRD (see Table 1).2,3 Black patients descending from the southern and western portions of Africa are most likely to have two alleles, putting them at the highest risk for hypertension and associated CKD.
Foster et al reported that black patients with two altered alleles had a 31% higher risk for CKD and ESRD, compared with individuals with hypertension-induced nephrosclerosis who had zero to one altered alleles.4 Nondiabetic black patients with CKD who have two altered alleles are at highest risk for focal segmental glomerulosclerosis, HIV nephropathy, and CKD attributable to hypertension.2 The African-American Study of Kidney Disease and Hypertension found that black patients with hypertension controlled by ACE inhibitors had slower progression of CKD, regardless of allele variation.5 Currently, there is no treatment for this genetic alteration.4
One could posit that black patients undergoing renal transplant would have a higher risk for renal failure in the transplanted kidney due to APOL1-related hypertension, compared to nonblack renal transplant recipients. Additionally, a donor kidney with an altered APOL1 gene may have a higher risk for failure.6
Genotyping for APOL1 (CPT code: 81479) is available in select laboratories at a cost of approximately $400.7 For a family that has a member affected by kidney failure at a young age, knowing whether the APOL1 gene is carried in the family would allow early aggressive hypertension management to help prevent a lifetime of severe CKD.
Susan E. Brown, MS, ARNP,
ACNP-BC, CCRN
Great River Nephrology,
West Burlington, Iowa
REFERENCES
1. United States Renal Data System. Annual data report: atlas of chronic kidney disease and end-stage renal disease in the United States (2012). www.usrds.org/2012/view/v1_01.aspx. Accessed October 19, 2014.
2. Kopp JB, Nelson GW, Sampath K, et al. APOL1 genetic variants in focal segmental glomerulosclerosis and HIV-associated nephropathy.
J Am Soc Nephrol. 2011;22(11):2129-2137.
3. Parsa A, Kao L, Xie D, et al; AASK and CRIC Study Investigators. APOL1 risk variants, race and progression of chronic kidney disease.
N Engl J Med. 2013;369:2183-2196.
4. Foster MC, Coresh J, Fornage M, et al. APOL1 variants associate with increased risk of CKD among African Americans. J Am Soc Nephrol. 2013;24(9):1484-1491.
5. Lipkowitz MS, Freedman BI, Langefeld CD, et al; AASK Investigators. Apolipoprotein L1 gene variants associate with hypertension-attributed nephropathy and the rate of kidney function decline in African Americans. Kidney Int. 2013;83(1):114–120.
6. Reeves-Daniel AM, DePalma JA, Bleyer AJ, et al. The APOL1 gene and allograft survival after kidney transplantation. Am J Transplant. 2011;11(5):1025-1030.
7. Partners Healthcare Personalized Medicine. Order APOL1 genotyping test for non-diabetic nephropathy kidney disease. http://personalizedmedicine.partners.org/Laboratory-For-Molecular-Medicine/Ordering/Kidney-Disease/APOL1-Gene-Sequencing.aspx. Accessed October 19, 2014.
8. Grovas A, Fremgen A, Rauck A, et al. The National Cancer Data Base report on patterns of childhood cancers in the United States. Cancer. 1997;80(12):2321-2332.
9. Johns Hopkins Medicine. Wilm’s tumor. www.hopkinsmedicine.org/kimmel_cancer_center/centers/pediatric_oncology/cancer_types/wilms_tumor.html. Accessed October 19, 2014.
10. Dome JS, Huff V. Wilms tumor overview. In: Pagon RA, Adam MP, Ardinger HH, et al (eds). GeneReviews® [Internet]. Seattle, WA: University of Washington, Seattle; 1993-2014. www.ncbi.nlm.nih.gov/books/NBK1294/. Accessed October 19, 2014.
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12. Fernandez C, Geller JI, Ehrlich PF, et al. Renal tumors. In: Pizzo P, Poplack D (eds). Principles and Practice of Pediatric Oncology. 6th ed, St Louis, MO: Lippincott Williams & Wilkins. 2011; 861.
13. Metzger ML, Dome JS. Current therapy for Wilms’ tumor. Oncologist. 2005;10(10):815-826.