Alport Foundation of Australia
 


Which genes are affected in Alport Syndrome?


Three subdivisions of Alport exist:


  1. (1)Autosomal Dominant Alport Syndrome (ADAS)

  2. Quite rare, about 5% of individuals with AS.


A mutated gene exists on one of the numbered chromosomes. There are two copies of every chromosome, and the dominant mutated gene will override the working gene. However, this form of the disease progresses more slowly than other forms.


  1. (2)Autosomal Recessive Alport Syndrome (ARAS)

  2. About 15% of individuals with AS.


A recessive mutated gene on an autosome will be overridden by a working gene. Thus, for the offspring to develop AS, they must receive a recessive mutated gene from both parents.  If an individual has only one mutated recessive gene, then he/she is a carrier of AS, but will not usually develop the disease. Both males and females are affected equally with ARAS and may develop end stage renal disease (ESRD) by the age of 30.


  1. (3)X Linked Alport Syndrome (XLAS)

  2. 80% of individuals with AS.


There is a mutation in a gene carried on the X (female sex) chromosome. The problem is more severe in men (XY) than in women (XX), as generally females have one “good” X chromosome to protect them and one with XLAS, whereas male sufferers have only the one X chromosome, which is XLAS.  In this form the disease progresses more rapidly in males than in females, with ESRD usually occurring in males between the ages of 30 and 50.










Transfer Rules for XLAS to Next Generation:


Fathers pass a copy of their Y (male) chromosome to their sons. Thus sons of male XLAS sufferers have 0% chance of inheriting XLAS.  Fathers pass a copy of their X (female) chromosome to their daughters. Thus, daughters of male XLAS sufferers must have 100% chance of carrying XLAS.


All offspring (male and female) of  female Alport  carries have a 50% chance of receiving their mother’s XLAS chromosome, as the mother passes on only one of her two X chromosomes (X, or XLAS).


Why is it important to locate Alport sufferers?


An Alport carrier may be unaware of any problem, even at age 30. By then the mutation may have been passed on to the next generation. However, if we know that certain family members have XLAS then it is possible potentially to determine who in the family tree is at risk. Finding other living family members who may unknowingly have Alport Syndrome will benefit those people in two ways: firstly by early detection (a simple urine and blood test is a good start) treatment could be started much sooner, giving them better health outcomes and secondly, they may choose to discuss with their doctors or a geneticist the possibility of eliminating the disease from their descendants.


Treatment of Alport Syndrome


At present there is no cure for Alport Syndrome.


Certain blood pressure lowering medications are known to also decrease the amount of protein leakage from the kidneys.  Other medications may also be prescribed for individuals who exhibit further complications. The current aim of treatment is to slow the progress of the disease.


Hearing aids and lens replacement of the eye may be required in the treatment of some Alport sufferers.


A healthy diet consisting of low salt and low protein is usually recommended in order to ease the pressures on the kidney.


When kidney failure occurs dialysis is recommended, or transplantation may be an option for the patient.


There is well deserved optimism that current research will lead to reversal/cure.  It is early days for this, but when something comes through it is most important to find people who can benefit from current developments.  See for example this project:


http://www.medscape.com/viewarticle/539047


Some Informative Articles:


There are many articles on XLAS, e.g. “Hereditary_nephritis_-_Alport_Syndrome.pdf” available here:

http://www.kidney.org.au/PatientInformation/HealthFactSheets/tabid/609/ItemId/292/Default.aspx


Also see:

“Winding Back the Clock with Kidney Stem Cells” - Dr Sharon Ricardo


http://en.wikibooks.org/wiki/Handbook_of_Genetic_Counseling/Alport_Syndrome#Support_groups

ALPORT SUPPORT GROUP INAUGURAL MEETING was held on Saturday 12th September 2009 View movie presentations about Alport SyndromeDR_PARKIN_MOVIE.htmlshapeimage_5_link_0

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Alport Syndrome is a hereditary kidney disease, (sometimes referred to as hereditary nephritis) which eventually causes renal failure and sometimes other symptoms, such as deafness and vision problems.


Symptoms of Alport Syndrome include blood in the urine (may not be visible), protein in the urine (trace to large amounts), high blood pressure, possible deafness and possible vision problems. The degree of symptoms varies between families and also between sexes, as female sufferers may have very mild symptoms. The outcome for males is usually more severe, with 90% of males suffering renal failure by the age of forty.


Why are the kidneys, ears and eyes affected in Alport Syndrome?


Firstly we need to understand that the body is held together by connective tissue and this connective tissue is made up of “collagen”, which itself consists of strands of proteins assembled like the strands in a rope. There are many “types “of collagen throughout the body, and type IV collagen is found only in basement membranes of the glomerulus (the filter) of the kidney, the cochlea of the ear and the lens of the eye.


Specific genes carry the information (or pattern) for the “knitting together” of the strands of protein to form collagen.  Hence any mutation in a “type IV” pattern carrying gene will have the potential to affect the ear, the eye and the kidney. The most serious problems arise from impairment of the glomerulus of the kidney.

ALPORT SYNDROME BACKGROUND