Types of Alport Syndrome
ADAS is the rarest form of Alport syndrome, accounting for about 5% of all cases. A single inherited copy of the mutated gene can cause the disease. Generally, at least one parent will have shown symptoms of Alport syndrome. ADAS is comparable to XLAS in symptoms, although men and women experience similar disease progression and severity, and kidney failure typically occurs later in life.
ARAS is the second most common type of Alport syndrome, affecting the genes COL4A3 and COL4A4 on chromosome 2. As it is an autosomal recessive disease, people only develop ARAS if they inherit two copies of the disease-causing mutation, one from each parent, on the autosomal chromosomes. Autosomal recessive disease affects men and women equally.
XLAS is the most common type of Alport syndrome, representing about 80% of diagnosed cases. In XLAS, the mutated disease-causing gene is situated on the X-chromosome (COL4A5). Men, having only one X-chromosome, are affected more severely, because they have only one copy of this gene.