Alport syndrome

 ICD9           = 759.89|
 ICDO           = |
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 Caption        = |
 OMIM           = 301050 |
 OMIM_mult      = 104200203780300195|
 MedlinePlus    = 000504 |
 eMedicineSubj  = med |
 eMedicineTopic = 110 |
 DiseasesDB     = 454 |

}} Alport syndrome is a geneticcondition characterized by the progressive loss of kidneyfunction and hearing. Alport syndrome can also affect the eyes. The presence of bloodin the urine(hematuria) is almost always found in this condition.

It was first identified in a British family by Dr. Cecil A. Alportin 1927.

Causes

Alport syndrome is caused by mutationsin COL4A3, COL4A4, and COL4A5, collagenbiosynthesis genes. Mutations in any of these genes prevent the proper production or assembly of the type IV collagen network, which is an important structural component of basement membranes in the kidney, inner ear, and eye. Basement membranes are thin, sheet-like structures that separate and support cells in many tissues. When mutations prevent the formation of type IV collagen fibers, the basement membranes of the kidneys are not able to filter waste products from the blood and create urine normally, allowing blood and proteininto the urine. The abnormalities of type IV collagen in kidney basement membranes cause gradual scarring of the kidneys, eventually leading to kidney failure in many people with the disease.

Inheritance patterns

Alport syndrome can have different inheritance patterns that are dependent on the genetic mutation.

• In most people with Alport syndrome, the condition is inherited in an X-linkedpattern, due to mutations in the COL4A5 gene. A condition is considered X-linked if the gene involved in the disorder is located on the X chromosome. In males, who have only one X chromosome, one altered copy of the COL4A5 gene is sufficient to cause severe Alport syndrome, explaining why all affected males develop kidney failure eventually. In females, who have two X chromosomes, a mutation in one copy of the COL4A5 gene results in blood in the urine, but most affected females do not develop kidney failure. A striking characteristic of X-linked inheritance is that fathers cannot pass X-linked diseases to their sons.

• Alport syndrome can be inherited in an autosomal recessivepattern if both copies of the COL4A3 or COL4A4 gene, located on chromosome 2, have been mutated. Most often, the parents of a child with an autosomal recessive disorder are not affected but are carriers of one copy of the altered gene.

Criteria for the clinical diagnosis

Gregory et al, 1996, give the following 10 criteria for the diagnosis of Alport syndrome, 4 of the 10 criteria must be met:

• Family history of nephritisof unexplained haematuria in a first degree relative of the index caseor in a male relative linked through any numbers of females.
• Persistent haematuria without evidence of another possibly inherited nephropathy such as thin GBM disease, polycystic kidney diseaseor IgA nephropathy.
• Bilateral sensorineural hearing lossin the 2000 to 8000 Hz range. The hearing loss develops gradually, is not present in early infancy and commonly presents before the age of 30 years.
• A mutationin COL4An(where n = 3, 4 or 5).
• Immunohistochemicalevidence of complete or partial lack of the Alport epitopein glomerular, or epidermal basement membranes, or both.
• Widespread GBMultrastructural abnormalities, in particular thickening, thinning and splitting.
• Ocular lesions including anterior lenticonus, posterior subcapsular cataract, posterior polymorphous dystrophyand retinal flecks.
• Gradual progression to ESRDin the index case of at least two family members.
• Macrothrombocytopeniaor granulocytic inclusions.
• Diffuse leiomyomatosisof esophagusor female genitalia, or both.

References

• Kashtan CE. Michael AF. Alport syndrome. Kidney International. 50(5):1445-63, 1996 Nov.[1]
• Tryggvason K. Heikkila P. Pettersson E. Tibell A. Thorner P. Can Alport syndrome be treated by gene therapy?. Kidney International. 51(5):1493-9, 1997 May.
• Gregory MC et al: Alport syndrome clinical phenotypes, incidence and pathology, in Molecular Pathology and Genetics of Alport Syndrome (vol 117), edited by Tryggvason K, Basel, Karger, 1996, pp 1-28

This article incorporates public domain text from The U.S. National Library of Medicinede:Alport-Syndrom es:Síndrome de Alport fr:Néphropathies par anomalie du collagène IV pt:Síndrome de Alport

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Alport+syndrome Wikipedia article Alport syndrome.