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What is Alport syndrome?
Alport syndrome is a genetic kidney disease caused by mutations in the genes COL4A3, COL4A4, and COL4A5 that determine how we produce type 4 collagen which is present in the kidney, the inner ear and the eyes.
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Alport syndrome is considered a rare disease, although researchers currently believe the prevalence is probably more than reported since the disease is often undiagnosed in women with mild symptoms.
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Alport syndrome causes kidney disease, hearing loss and eye abnormalities.
What are the Symptoms of Alport syndrome?
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Blood in the urine (which not be visible)
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Protein in the urine (ranging from trace to large amounts)
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A significant deterioration in renal function
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High blood pressure
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Possible hearing loss
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Possible vision problems (lenticonus and retinal spots or flecks)
The degree of symptoms varies according to the pattern of inheritance. There are three types of Alport syndrome:
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X-linked Alport syndrome (XLAS), around 1 in 5,000 of general population
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Autosomal recessive Alport syndrome (ARAS), around 1 in 40,000 of general population
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Autosomal dominant Alport syndrome (ADAS),around 1 in 100 of general population
Family members sharing the same inheritance of the disease may experience symptoms to a greater or lesser degree.
The most commonly diagnosed form of Alport syndrome is X-linked or sex-linked Alport, meaning that the mutated gene is located on one of the two sex chromosomes, the X chromosome. The symptoms of X-linked Alport syndrome are more severe in men than in women, since men only have one X chromosome.
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The outcome for males is often more severe, with 90% of males suffering renal failure by 40 years of age. Renal failure requires patients to undergo frequent kidney dialysis and eventually a renal transplant. If anyone in your family is diagnosed with Alport syndrome, it is vital that all family members, male and female, investigate the possibility that they too have inherited the disease. Genetic counselling is recommended, along with genetic testing whenever possible. In Australia the cost of genetic testing is subsidised by Medicare. Consult your doctor for more information regarding genetic testing for Alport syndrome.
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For more information about the inheritance patterns, and why you have Alport syndrome, visit the Awareness pages of this website.​​​
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Why are the kidneys, ears and eyes affected by Alport syndrome?
The body is held together by connective tissue, which is made up of collagen. Collagen consists of strands of proteins assembled like the strands in a rope. Specific genes carry the information (or pattern) for the "knitting together" of the strands of protein to form collagen. There are many types of collagen throughout the body, and collagen type 4 is found only in the basement membranes of the glomerulus (the filter) of the kidney, the cochlea of the ear, and the lens of the eye.
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Mutated collagen genes (COL4A3, COL4A4 or COL4A5) have the potential to affect the ears, the eyes, and the kidneys because the type 4 collagen does not form correctly. The most serious problems arise from impairment, or scarring, of the glomerulus of the kidney as it severely weakens the ability of the glomerulus to filter waste from the blood, causing symptoms such as blood (haematuria) and protein (proteinuria or albuminuria) in the urine. The presence of blood and protein can be detected in the urine from an early age, and becomes more evident as the disease progresses. The deterioration of the glomerulus worsens, and eventually regular kidney dialysis, or a kidney transplant, is required.​
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Sensorineural hearing loss is a common symptom of Alport syndrome, however in some it is very mild and some patients have no significant loss at all. It is an abnormality of the structure in the inner ear that transforms sound into nerve impulses. Hearing is normal at birth but gradually deteriorates with age, usually being detected in late childhood or adolescence. Consultation with a qualified audiologists can diagnose, prescribe and fit hearing aids that will greatly improve hearing and patient well being.
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Abnormal lens shape, anterior lenticonus, may also be associated with Alport syndrome. It occurs in 15 to 20% of patients and causes distorted vision. An ophthalmologist should be seen to screen the eyes for disease, and lens replacements may be recommended. Retinal flecks, which have no detrimental affect on vision, can be seen on retinal imaging. These flecks are unique to Alport syndrome.
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Diagnosis of Alport syndrome
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There are several methods of diagnosing Alport syndrome. A complete medical history and physical exam can indicate the early symptoms of the disease. Blood and urine analysis can indicate abnormalities in how the body filters waste products.
Skin or kidney biopsies can be used to test for abnormalities in type 4 collagen by staining the tissue for the protein and examining the tissue under a microscope.
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Hearing tests can determine whether patients are experiencing hearing loss, though this test on its own cannot definitively point to Alport syndrome.
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The lens and retina abnormalities caused by Alport syndrome are visible in a dilated eye exam.
The surest method of diagnosing Alport syndrome is genetic testing for mutations in COL4A3, COL4A4, and COL4A5 genes. This genetic test can be done on a tissue biopsy, a kidney biopsy, or a blood sample.
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