Alport syndrome is a hereditary disease that typically affects the production of type IV collagen, a protein responsible for maintaining kidney function and for providing structural support to the eyes and ears.
The severity of the symptoms and life expectancy can vary greatly among Alport syndrome patients depending on the type of disease they have.
Gender-based differences in Alport syndrome
Alport syndrome can be caused by mutations in three different genes encoding for type IV collagen: COL4A5, COL4A3, and COL4A4.
COL4A5 is situated on the X chromosome, one of the two sex chromosomes, while COL4A3 and COL4A4 are situated on chromosome 2 or a so-called autosome.
We all have two copies of each chromosome, one inherited from each parent. The only difference is with the sex chromosomes since females have two copies of the X chromosome while males have one X and one Y chromosome.
So depending on which gene is mutated in Alport syndrome, the condition can either be inherited in an X-linked manner (associated with 80 to 85 percent of Alport syndrome cases), meaning that males will be more severely affected than females, since they only have one copy of the X chromosome, or inherited in an autosomal recessive or dominant manner.
Autosomal recessive means that both parents are carriers of the disease and must pass on one mutated copy of the disease-causing gene to their children for them to develop the disease. In approximately 15 percent of cases, Alport syndrome is inherited in an autosomal recessive pattern.
Autosomal dominant inheritance is when only one mutated copy of the gene is sufficient to cause the disease to develop. Alport syndrome can be inherited through this pattern, though this tends to be very rare, and the mechanisms are not well understood.
In both autosomal inheritance patterns, males and females tend to be equally affected.
Prognosis
Women affected by Alport syndrome generally have a normal lifespan. Typically, the only symptom experienced by female patients is hematuria or the presence of blood in the urine. In extreme instances, elevated blood pressure, swelling, and hearing loss may arise as complications during pregnancy.
Symptoms of the disease typically appear in male patients during childhood and can progressively escalate in severity. Most affected individuals will experience end-stage renal disease and deafness by age 40. Without regular dialysis treatments or renal transplant, a patient’s life expectancy may be reduced.
Treatment options
There is currently no cure for Alport syndrome. However, research is ongoing to determine potential treatments that may delay end-stage renal disease and increase life expectancy in males with X-linked recessive Alport syndrome.
It is recommended that affected individuals work with a kidney specialist for the long-term management of the symptoms and diseases associated with Alport syndrome, as lifestyle changes such as a diet low in sodium can help manage the condition.
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