- Alport syndrome, X-linked
- Hemorrhagic familial nephritis
- Hemorrhagic hereditary nephritis
- Congenital hereditary hematuria
Your QuestionMy sister's daughter has a son with X-linked Alport syndrome. Although my niece was not genetically tested as a carrier, her doctor assumed she is a carrier because of the large amount of blood in her urine. I have 2 sons and one daughter. I am told that my sons cannot be carriers and therefore don't have to worry about passing on this syndrome. Is that true? Also, how about my daughter? I have not been tested but if I do get tested and am not a carrier, then can I assume she is ok and will not pass down the syndrome to her children? Also, if I have my urine tested for hematuria and I don't have blood, can I assume that I am not a carrier?
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Questions on this page
- How is Alport syndrome inherited?
- Can males be unaffected carriers of X-linked Alport syndrome?
- Are the maternal female cousins of a male with X-linked Alport syndrome at risk to be carriers?
- If a woman is not a carrier for X-linked Alport syndrome, are her grandchildren at risk to be affected?
- How can I determine whether I am a carrier of X-linked Alport syndrome?
- How can I find a genetics professional in my area?
In approximately 15 percent of cases, Alport syndrome results from mutations in both copies of the COL4A3 or COL4A4 gene and is inherited in an autosomal recessive pattern. The parents of an individual with the autosomal recessive form of this condition each have one copy of the mutated gene and are called carriers. Some carriers are unaffected and others develop a less severe condition called thin basement membrane nephropathy, which is characterized by hematuria.
Alport syndrome has an autosomal dominant pattern of inheritance in about 5 percent of cases. People with this form of Alport syndrome have one mutation in either the COL4A3 or COL4A4 gene in each cell. It remains unclear why some individuals with one mutation in the COL4A3 or COL4A4 gene have autosomal dominant Alport syndrome and others have thin basement membrane nephropathy.
The mother of a male with XLAS should have a urinalysis and/or molecular genetic testing if the mutation has been identified in her son. The presence of hematuria generally indicates that she is likely to be a carrier of XLAS. If the mother of an affected male is indeed a carrier of XLAS, the maternal female cousins are also at risk to be carriers of XLAS. Whether their children are at risk would likewise depend on whether they are carriers.
Individuals interested in learning about specific genetic risks to themselves or family members should speak with a genetics professional.
Individuals interested in determining the genetic risk and status for themselves or family members should speak with a genetics professional to determine whether they are at risk and/or the type of testing that is indicated.