Alport Syndrome

Alport Syndrome

National Organization for Rare Disorders, Inc.

Important

It is possible that the main title of the report Alport Syndrome is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.

Synonyms

  • Hereditary Nephritis
  • Nephritis and Nerve Deafness, Hereditary
  • Nephropathy and Deafness, Hereditary
  • Hematuria-Nephropathy Deafness
  • Hemorrhagic Familial Nephritis
  • Hereditary Deafness and Nephropathy
  • Hereditary Nephritis With Sensory Deafness
  • Congenital hereditary hematuria

Disorder Subdivisions

  • Autosomal Dominant Alport Syndrome (ADAS)
  • Autosomal Recessive Alport Syndrome (ARAS)
  • X-Linked Alport Syndrome (XLAS)

General Discussion

Alport syndrome is a group of hereditary disorders characterized by progressive deterioration of parts of the kidney known as basement membranes. This deterioration may lead to chronic kidney (renal) disease. Eventually, severe renal failure (end-stage renal disease or ESRD) may develop. Some types of Alport syndrome may also affect vision and hearing. Most cases of Alport syndrome have an X-linked pattern of inheritance.

Symptoms

Some individuals do not exhibit symptoms (asymptomatic). When symptoms are present, they can vary widely. In most cases, they are progressive.



The more common early symptoms are an abnormal urine color due to serum proteins or red blood cells in the urine. These signs suggest a decline in kidney's filtering function. Loss of hearing and/or loss of vision may occur. Hearing and vision problems tend to affect males more often than females.



As the disease progresses, the affected individual's legs may swell. There may also be swelling around the eyes.



Uremia occurs when the kidneys fail to remove waste products from the blood. Upset stomach, which may vary from loss of appetite to severe pain, can occur along with nausea, vomiting of food and blood, weakness, fatigue, excessive need for sleep, and dry, often itchy, skin. A urine-like smell on the breath, pale skin (pallor), shortness of breath, hypertension, and fluid retention may also occur.



As the disease progresses, it can lead to chronic heart failure and end-stage renal disease, requiring regular dialysis.



Abnormalities of the eye may occur in certain forms of Alport syndrome. The surface of the eye's lens may be cone-shaped (lenticonus) or spherical (spherophakia). The lens of the eye may be opaque or cloudy (cataracts). White dots may appear on the retina (retinal macular flecks). Children with Alport syndrome are often very nearsighted (myopic).

Causes

Most (about 85 percent) cases of Alport syndrome exhibit the X-linked pattern of inheritance. Almost all of those affected are male. Of the remaining cases, most have an autosomal recessive pattern of inheritance. In a small number of cases, the inheritance pattern is autosomal dominant.



Alport syndrome is caused by mutations of genes involved in the production of proteins known as collagens. The genetic defect associated with the classical form of the syndrome (XLAS) has been tracked to a site on the X chromosome (Xq22). Another form (ARAS) is associated with mutations on the long arm of chromosome 2 (2q36-q37). A third type (ADAS) may be linked to a site on chromosome 11 (11q24).



Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Human body cells normally have 46 chromosomes. Pairs of human chromosomes are numbered from 1 through 22, and the sex chromosomes are designated X and Y. Males have one X and one Y chromosome and females have two X chromosomes. Each chromosome has a short arm (p) and a long arm (q). Chromosomes are further sub-divided into many bands that are numbered. For example, chromosome 2q36-q37 refers to the region between bands 36 and 37 on the long arm of chromosome 2. Similarly, chromosome Xq22 refers to band 22 of the X chromosome. The numbered bands specify the location of the thousands of genes that are present on each chromosome.



Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother.



Recessive genetic disorders occur when an individual inherits the same abnormal gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the defective gene and, therefore, have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive normal genes from both parents and be genetically normal for that particular trait is 25%. The risk is the same for males and females.



All individuals carry a few abnormal genes. Parents who are close relatives (consanguineous) have a higher chance than unrelated parents to both carry the same abnormal gene, which increases the risk to have children with a recessive genetic disorder.



Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary for the appearance of the disease. The abnormal gene can be inherited from either parent, or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from affected parent to offspring is 50% for each pregnancy regardless of the sex of the resulting child.



X-linked recessive genetic disorders are conditions caused by an abnormal gene on the X chromosome. Females have two X chromosomes but one of the X chromosomes is turned off and all of the genes on that chromosome are inactivated. Females who have a disease gene present on one of their X chromosomes are carriers for that disorder. Carrier females usually do not display symptoms of the disorder because it is usually the X chromosome with the abnormal gene that is turned off. A male has one X chromosome, and if he inherits an X chromosome that contains a disease gene, he will develop the disease. Males with X-linked disorders pass the disease gene to all of their daughters, who will be carriers. A male cannot pass an X-linked gene to his sons because males always pass their Y chromosome instead of their X chromosome to male offspring. Female carriers of an X-linked disorder have a 25% chance with each pregnancy to have a carrier daughter like themselves, a 25% chance to have a non-carrier daughter, a 25% chance to have a son affected with the disease, and a 25% chance to have an unaffected son.



X-linked dominant disorders are also caused by an abnormal gene on the X chromosome, but in these rare conditions, females with an abnormal gene are affected with the disease. Males with an abnormal gene are more severely affected than females, and many of these males do not survive.

Affected Populations

The prevalence rate for Alport syndrome is approximately 1 in 50,000 newborns.



The more common X-linked form of Alport syndrome affects mainly males. About 15% of newborns affected by Alport syndrome have no family history of kidney disease. There appear to be no racial or geographic concentrations related to this syndrome.

Standard Therapies

Diagnosis

In suspected cases of Alport syndrome, electron microscopy of a sample of kidney tissue may be performed to evaluate the condition of the basement membrane. Progressive loss of kidney function accompanied by loss of hearing is a clue to diagnosis.



Treatment

Hearing aids may be required for deafness and corrective surgery for vision problems. Renal function and certain components in the blood are regularly monitored. No treatment prevents the progression of renal failure. Dialysis and/or transplantation may be initiated when ESRD develops. Dialysis involves removing blood from the patient's artery, cleansing it of unwanted substances that would normally be excreted in the urine, and returning the cleansed blood to a vein.



If kidney transplantation is indicated, great care must be taken in selecting living related kidney donors because of the slight or in apparent disease in some female family members.



Genetic counseling will be of benefit for patients and their families. Other treatment is symptomatic and supportive.

Investigational Therapies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website.



For information about clinical trials being conducted at the National Institutes of Health (NIH) in Bethesda, MD, contact the NIH Patient Recruitment Office:



Tollfree: (800) 411-1222

TTY: (866) 411-1010

Email: prpl@cc.nih.gov



For information about clinical trials sponsored by private sources, contact:

www.centerwatch.com

References

TEXTBOOKS

Chadha V, Warady BA. Alport Syndrome. In: NORD Guide to Rare Disorders. Lippincott Williams & Wilkins. Philadelphia, PA. 2003:680.



Beers MH, Berkow R, eds. The Merck Manual, 17th ed. Whitehouse Station, NJ: Merck Research Laboratories; 1999:1906.



Berkow R, ed. The Merck Manual-Home Edition.2nd ed. Whitehouse Station, NJ: Merck Research Laboratories; 2003:856.



Brenner BM, Rector Jr FC. The Kidney. 4th ed. W.B. Saunders Company. Philadelphia, PA; 1991:1331-34.



Scriver CR, Beaudet AL, Sly WS, et al., eds. The Metabolic Molecular Basis of Inherited Disease. 8th ed. McGraw-Hill Companies. New York, NY; 2001:5453-63.



REVIEW ARTICLES

Kashtan CE. Familial hematuria due to type IV collagen mutations: Alport syndrome and thin basement membrane nephropathy. Curr Opin Pediatr. 2004;16:177-81.



Imai E, Isaka Y. Perspectives for gene therapy in renal diseases. Intern Med. 2004;43:85-96.



Ben-Yosef T, Friedman TB. The genetic bases for syndromic and nonsyndromic deafness among Jews. Trends Mol Med. 2003;9:496-502.



Savige J, Rana K, Tonna S, et al. Thin basement membrane nephropathy. Kidney Int. 2003;64:1169-78.



Hanss B, Bruggeman LA. Applications of gene therapy to kidney disease. Curr Opin Nephrol Hypertens. 2003;12:439-45.



Pescucci C, Longo I, Bruttini M, et al. Type IV collagen related diseases. J Nephrol. 2003;16:314-16.



JOURNAL ARTICLES

Charytan D, Torre A, Khurana M, et al. Allograft rejection and glomerular basement membrane antibodies in Alport syndrome. J Nephrol. 2004;17:431-35.



Pescucci C, Mari F, Longo I, et al. Autosomal-dominant Alport syndrome: natural history of a disease due to COL4A3 or COL4A4 gene. Kidney Int. 2004;65:1598-603.



Czarny-Ratajczak M, Latos-Bielenska A. Collagens, the basic protein of the body. J Appl Genet. 2000;41:317-30.



Jais JP, Kneebelmann B, Giatra I, et al. X-linked Alport syndrome: natural history and genotype-phenotype correlations in girls and women belonging to 195 families: a "European Community Alport Syndrome Concerted Action" study. J Am Soc Nephrol. 2003;14:2603-10.



Prakash S, Chung KW, Sinha S, et al. Autosomal dominant progressive neuropathy with deafness: linkage to a new locus on chromosome 11q24. J Am Soc Nephrol. 2003;14:1794-803



FROM THE INTERNET

McKusick VA, ed. Online Mendelian Inheritance in Man (OMIM). The Johns Hopkins University. Alport Syndrome, X-Linked; ATS. Entry Number; 301050: Last Edit Date; 12/17/2003.



McKusick VA, ed. Online Mendelian Inheritance in Man (OMIM). The Johns Hopkins University. Alport Syndrome, Autosomal Recessive. Entry Number; 203780: Last Edit Date; 3/14/2000.



McKusick VA, ed. Online Mendelian Inheritance in Man (OMIM). The Johns Hopkins University. Alport Syndrome, Autosomal Dominant. Entry Number; 104200: Last Edit Date; 3/17/2004.



Agha IA. Medical Encyclopedia: Alport Syndrome. MedlinePlus. Update Date: 1/19/2004. 3pp.

www.nlm.nih.gov/medlineplus/ency/article/000504.htm



Kashtan CE. Alport Syndrome. Gene Reviews. Last Revision: 29 December 2003. 22pp.

www.genetests.org



National Kidney Foundation. A to Z Health Guide - Alport Syndrome. ©2004. 3pp.

www.kidney.org/atoz/atozPrint.cfm?id=47



Alport syndrome-Genetics Home Reference



http://ghr.nlm.nih.gov/condition=alportsyndrome/show/print

Resources

American Kidney Fund, Inc.

11921 Rockville Pike

Suite 300

Rockville, MD 20852

USA

Tel: (800)638-8299

Email: helpline@kidneyfund.org

Internet: http://www.kidneyfund.org



National Kidney Foundation

30 East 33rd Street

New York, NY 10016

Tel: (212)889-2210

Fax: (212)689-9261

Tel: (800)622-9010

Email: info@kidney.org

Internet: http://www.kidney.org



Urology Care Foundation

1000 Corporate Blvd

Linthicum, MD 21090

USA

Tel: (410)689-3700

Fax: (410)689-3896

Tel: (800)828-7866

Email: Info@UrologyCareFoundation.org

Internet: http://www.urologyhealth.org/



NIH/National Kidney and Urologic Diseases Information Clearinghouse

3 Information Way

Bethesda, MD 20892-3580

Fax: (703)738-4929

Tel: (800)891-5390

TDD: (866)569-1162

Email: nkudic@info.niddk.nih.gov

Internet: http://www.kidney.niddk.nih.gov/



Genetic and Rare Diseases (GARD) Information Center

PO Box 8126

Gaithersburg, MD 20898-8126

Tel: (301)251-4925

Fax: (301)251-4911

Tel: (888)205-2311

TDD: (888)205-3223

Internet: http://rarediseases.info.nih.gov/GARD/



Madisons Foundation

PO Box 241956

Los Angeles, CA 90024

Tel: (310)264-0826

Fax: (310)264-4766

Email: getinfo@madisonsfoundation.org

Internet: http://www.madisonsfoundation.org



Let Them Hear Foundation

1900 University Avenue, Suite 101

East Palo Alto, CA 94303

Tel: (650)462-3174

Fax: (650)462-3144

Email: info@letthemhear.org

Internet: http://www.letthemhear.org



Perkins School for the Blind

175 North Beacon Street

Watertown, MA 02472

Tel: (617)924-3434

Fax: (617)926-2027

Email: Info@Perkins.org

Internet: http://www.Perkins.org



National Consortium on Deaf-Blindness

The Teaching Research Institute

345 N. Monmouth Avenue

Monmouth, OR 97361

Tel: (800)438-9376

Fax: (503)838-8150

Tel: (800)438-9376

TDD: (800)854-7013

Email: info@nationaldb.org

Internet: http://www.nationaldb.org



Kidney & Urology Foundation of America, Inc.

2 West 47th Street

Suite 401

New York, NY 10036

Tel: (212)629-9770

Fax: (212)629-5652

Tel: (800)633-6628

Email: info@kidneyurology.org

Internet: http://www.kidneyurology.org



Alport Syndrome Foundation

1608 E. Briarwood Terrace

Phoenix, AZ 85048-9414

Tel: (480)460-0621

Fax: (480)460-0621

Email: info@alportsyndrome.org

Internet: http://www.alportsyndrome.org



For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders, Inc.® (NORD). Cigna members can access the complete report by logging into myCigna.com. For non-Cigna members, a copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see http://www.rarediseases.org/search/rdblist.html.

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