How common is Alport syndrome?
As a rare disease, the prevalence of Alport syndrome is not well-known, although it is estimated to be 1 in every 50,000 live births worldwide. In the U.S., it is believed to affect 1 in every 5,000 people, while across Europe that estimate ranges from 1 in 100,000 people to 1 in every 11,000.
Elsewhere, a study in 2,935 patients with chronic kidney disease in Australia, published in the Orphanet Journal of Rare Diseases in 2014, identified five among that group as being having Alport syndrome. From this data, researchers estimated the prevalence of Alport in the general adult population in Australia to be about 2.4 people out of every 1 million.
For this rare disease, no clear evidence exists to date suggesting or showing a variation among ethnic groups.
Prevalence of Alport syndrome types
About 85 percent of Alport syndrome cases are X-linked, with the remainder (about 15 percent) being autosomal recessive Alport syndrome (ARAS). Only a few cases of autosomal dominant Alport syndrome (ADAS) have been reported, so no estimates of percentages are available.
XLAS, or X-linked Alport, is clearly the most common disease form. In general, this means that Alport syndrome is more common and more severe in men than in women, because men have only one X chromosome and it carries the mutation. Women who carry the mutation causing XLAS may never show any symptoms of the disease, but have a 50 percent risk of passing the mutated gene to a child.
Prevalence of Alport symptoms
Eye abnormalities are present in about 30 percent of all Alport cases, regardless of disease type.
Male patients with XLAS are usually more severely affected and show evidence of blood in their urine early in life (around age 3.5), followed by protein in the urine. These patients usually progress to end-stage kidney disease before age 40. Progression is milder in most female patients, with symptoms first appearing around age 9.
For patients with autosomal Alport syndrome (either dominant or recessive), disease symptoms are equally severe in both sexes, with early symptoms typically beginning between ages 3 and 4, and kidney disease progressing to kidney failure at about age 40.
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