Alport syndrome facts*
*Alport syndrome facts medical author: Melissa Conrad Stöppler, MD
- Alport syndrome is a genetic (inherited) disease.
- Signs and symptoms of Alport syndrome include hearing loss, eye problems, and blood in the urine, signifying loss of kidney function.
- Alport syndrome occurs in 1 out of 50,000 newborns.
- Mutations in the genes COL4A3, COL4A4, and COL4A5 cause Alport syndrome. These genes code for proteins responsible for the formation of a component of collagen Type IV.
- Different patterns of genetic inheritance have been observed in Alport syndrome.
- About 80% of cases of Alport syndrome are inherited in an X-linked manner (meaning the gene defect is on the X chromosome). About 15% of cases show autosomal recessive inheritance, and about 5% of cases are inherited in an autosomal dominant manner.
- Congenital hereditary hematuria is another name for Alport syndrome.
What is Alport syndrome?
What are the signs and symptoms of Alport syndrome?
People with Alport syndrome experience progressive loss of kidney function. Almost all affected individuals have blood in their urine (hematuria), which indicates abnormal functioning of the kidneys. Many people with Alport syndrome also develop high levels of protein in their urine (proteinuria). The kidneys become less able to function as this condition progresses, resulting in end-stage renal disease (ESRD).
People with Alport syndrome frequently develop sensorineural hearing loss, which is caused by abnormalities of the inner ear, during late childhood or early adolescence. Affected individuals may also have misshapen lenses in the eyes (anterior lenticonus) and abnormal coloration of the light-sensitive tissue at the back of the eye (retina). These eye abnormalities seldom lead to vision loss.
Significant hearing loss, eye abnormalities, and progressive kidney disease are more common in males with Alport syndrome than in affected females.
What genes are related to Alport syndrome?
Mutations in the COL4A3, COL4A4, and COL4A5 genes cause Alport syndrome. These genes each 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.
How do people inherit Alport syndrome?
Alport syndrome can have different inheritance patterns. About 80 percent of cases are caused by mutations in the COL4A5 gene and are inherited in an X-linked pattern. This gene is located on the X chromosome, which is one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the COL4A5 gene in each cell is sufficient to cause kidney failure and other severe symptoms of the disorder. In females (who have two X chromosomes), a mutation in one copy of the COL4A5 gene usually only results in hematuria, but some women experience more severe symptoms. A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.
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 autosomal dominant 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.
What other names do people use for Alport syndrome?
- congenital hereditary hematuria
- hematuria-nephropathy-deafness syndrome
- hematuric hereditary nephritis
- hemorrhagic familial nephritis
- hemorrhagic hereditary nephritis
- hereditary familial congenital hemorrhagic nephritis
- hereditary hematuria syndrome
- hereditary interstitial pyelonephritis
- hereditary nephritis
Latest MedicineNet News
Daily Health News
Health Solutions From Our Sponsors
"Alport Syndrome." Genetics Home Reference. 25 Feb. 2014.
Top Alport Syndrome Related Articles
BlindnessBlindness is the state of being sightless. Causes of blindness include macular degeneration, stroke, cataract, glaucoma, infection and trauma. Symptoms and signs may include eye pain, eye discharge, or the cornea or pupil turning white. Treatment of blindness depends upon the cause of the blindness.
Blood in UrineBlood in the urine is termed hematuria. Hematuria, whether it be gross or microscopic, is abnormal and should be further investigated.
Hearing LossHearing loss (deafness) may be present at birth or it may manifest later in life. Deafness may be genetic or due to damage from noise. Treatment of deafness depends upon its cause. Sensorineural hearing loss can be caused by conditions affecting the cochlea, eighth cranial nerve, spinal cord, or brain. Examples of conditions that can lead to sensorineural hearing loss include Meniere's disease, noise-induced hearing loss, hearing loss of aging (presbycusis), nerve injury from syphilis, hearing loss of unknown cause (idiopathic hearing loss), nerve tumors, and drug toxicity (such as aspirin and aminoglycosides).
Kidney Disease QuizKidney disease is common. Take this kidney disease quiz to test your knowledge and learn the symptoms, causes and types of kidney disease and what foods to eat and avoid!
Kidney (Renal) Failure
Kidney failure can occur from an acute event or a chronic condition or disease. Prerenal kidney failure is caused by blood loss, dehydration, or medication. Some of the renal causes of kidney failure include sepsis, medications, rhabdomyolysis, multiple myeloma, and acute glomerulonephritis.
Post renal causes of kidney failure include bladder obstruction, prostate problems, tumors, or kidney stones.Treatment options included diet, medications, or dialysis.
Kidneys PictureThe kidneys are a pair of organs located in the back of the abdomen. See a picture of the Kidneys and learn more about the health topic.