X-linked Alport syndrome
What is X-Linked Alport Syndrome?
Alport syndrome is a genetic condition characterized by progressive kidney disease, hearing loss, and abnormalities affecting the eyes. Alport syndrome can be inherited in an X-linked or autosomal recessive manner. The presentation of X-linked Alport syndrome is variable in severity; some individuals have a milder disease course, while others develop more severe disease with complications. The X-linked form of Alport syndrome is more severe in males than females.
Blood in the urine is often the first sign of kidney disease and typically presents during childhood. This is usually not detectable by the naked eye, but may be visible during periods of illness such as a cold or flu. Individuals with X-linked Alport syndrome also develop protein in the urine during childhood. Kidney disease often progresses to kidney failure by early adulthood. Kidney failure is associated with various symptoms including: high blood pressure, fatigue, poor appetite, swelling of legs and feet, and frequent urination. Kidney insufficiency and associated medical complications will develop in all males with X-linked Alport syndrome. Medications may delay the progress of kidney failure, but most often, either a kidney transplant and/or dialysis is necessary.
X-linked Alport syndrome is also associated with varying degrees of progressive hearing loss. The onset and severity of hearing loss is variable, but it is not uncommon for some degree of hearing loss to develop by adolescence.
Individuals with X-linked Alport syndrome may also develop eye abnormalities. Specific problems with the lens, retina and cornea are the most common in X-linked Alport syndrome and may result in light sensitivity, cataract formation, and blurred vision. Glasses are sometimes required to correct vision.
Limited information exists regarding vascular complications associated with Alport syndrome. However, aneurysms of the abdominal and thoracic aorta have been reported in a small number of males with Alport syndrome, in addition to aortic valve abnormalities. To date, vascular complications are believed to only occur in males. However, the frequency of vascular events remains unclear.
Most female carriers of X-linked Alport syndrome will have blood in the urine that is not detectable to the naked eye. Some females are also affected by varying degrees of hearing loss, but it tends to occur later in life. By late adulthood, up to 40% of female carriers will progress to kidney failure.
How common is X-Linked Alport Syndrome?
Collectively, all forms of Alport syndrome are estimated to occur in approximately 1 in 50,000 live births. X-linked Alport syndrome is the most common form, accounting for around 85% of all Alport syndrome. X-linked Alport syndrome occurs at a similar frequency amongst all ethnicities. Approximately 10-15% of males affected by X-linked Alport syndrome do not inherit a mutation from a carrier mother (de novo mutation).
How is X-Linked Alport Syndrome treated?
Currently, there is no cure for X-linked Alport syndrome. However, treatments are available to address many of the associated symptoms. Medications are utilized to treat high blood pressure, reduce protein in the urine, and slow the progression of kidney disease. However, kidney failure will develop eventually in all males with X-linked Alport syndrome and in some females. Because the onset of kidney failure is variable, transplantation or dialysis may be required as early as the teenage years, but most often, necessary by adulthood.
Hearing aids may be required to treat hearing loss. Additionally, ophthalmologic intervention, such as cataract surgery, may be required for some individuals.
A multidisciplinary team of physicians, including: nephrologists, audiologists, ophthalmologists and other healthcare professionals will need to be involved in the ongoing treatment and management of individuals with X-linked Alport syndrome.
What is the prognosis for a person with X-Linked Alport Syndrome?
While the prognosis of X-linked Alport syndrome is variable, the vast majority of males develop kidney failure by 40 years of age. Renal transplantation and/or dialysis are typically successful as patients approach kidney failure. However, complications from kidney disease may still result in shortened life span. Hearing loss develops in the vast majority of males by 40 years. Many times, the eye complications associated with X-linked Alport syndrome do not cause any severe vision problems; although, cataract surgery and/or corrective lenses may be required.