What is Alport Syndrome?
Alport Syndrome is a genetic disorder characterized by glomerulonephritis, endstage kidney disease, and hearing loss. Alport Syndrome can also affect the eyes. In 1927, Dr. Cecil A. Alport first described the combination of progressive hereditary nephritis with sensorineural deafness.
The presence of blood in the urine (hematuria) is almost always found in this condition. Alport Syndrome is an inherited disease of the kidney that can also affect the inner ear (cochlea) and eye. Alport Syndrome is estimated to effect 1 in 50,000 people.
It is caused by genetic mutations that affect the type IV collagen family of proteins. Type IV collagen is a major part of important tissue structures called basement membranes that are present in all tissues including the kidney, inner ear, and eye. Generally, Alport Syndrome affects boys more than girls because 80% of the time the disease is passed on by a mutation on the X chromosome (called X-linked Alport Syndrome).
Manifestations:
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Microscopic Hematuria
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Brown, pink, or red urine (gross hematuria) for several days, associated with a cold or flu
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Protein in the urine (proteinuria) and high blood pressure
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Hearing loss
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Anterior lenticonus may have a slow progressive deterioration of vision requiring patients to change the prescription of their glasses frequently. This condition may also lead to cataract formation
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Some people with Alport Syndrome have abnormal pigment of the retina called dot-and-fleck retinopathy, but this does not result in any abnormalities of vision
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Recurrent corneal erosion is another eye proble
Alport Syndrome Treatment
There is no treatment that has been proven to prevent the development of kidney failure in people with Alport Syndrome. It is very important for people with Alport Syndrome to be examined regularly by a Nephrologist, so that effects of kidney disease, such as hypertension, can be identified early and treated. Regular hearing and vision evaluation is also important.
Medications:
Data from studies suggest the benefits from angiotensin-converting enzyme (ACE) inhibitors in reducing proteinuria (protein in the urine) and progression of renal disease.
ACE inhibitors that have been used to treat Alport Syndrome patients include, but are not limited to:
- Enalapril (Vasotec)
- Fosinopril (Monopril)
- Lisinopril (Zestril, Prinivil)
- Quinapril (Accupril)
Angiotensin receptor blockers (ARBs) have also been used in patients with proteinuria as ARBs were shown to delay progression to kidney failure.
ARBs that have been used to treat Alport Syndrome patients include, but are not limited to:
- Losartan (Cozaar)
- Candesartan (Atacand)
Genes Related to Alport Syndrome:
Mutations in the COL4A3, COL4A4, and COL4A5 genes cause Alport syndrome. Each of these genes provide instructions for making one component of a protein called type IV collagen. This protein plays an important role in the kidneys, specifically in structures called glomeruli. Glomeruli are clusters of specialized blood vessels that remove water and waste products from blood and create urine. Mutations in these genes result in abnormalities of the type IV collagen in glomeruli, which prevents the kidneys from properly filtering the blood and allows blood and protein to pass into the urine. Gradual scarring of the kidneys occurs, eventually leading to kidney failure in many people with Alport syndrome.
Type IV collagen is also an important component of inner ear structures, particularly the organ of Corti, that transform sound waves into nerve impulses for the brain. Alterations in type IV collagen often result in abnormal inner ear function, which can lead to hearing loss. In the eye, this protein is important for maintaining the shape of the lens and the normal color of the retina. Mutations that disrupt type IV collagen can result in misshapen lenses and an abnormally colored retina.
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