Alström Syndrome is a rare inherited condition classified as autosomal recessive, meaning that both gene copies must be affected for the disease to appear. It is caused by mutations in the ALMS1 gene, which prevent the gene from functioning as it should. The condition affects both males and females equally.

Each person carries two copies of almost every gene – one from each parent. Most parents are unaware they carry a change in the ALMS1 gene until they have a child diagnosed with the syndrome. Carriers have one altered copy of the gene but show no symptoms themselves, unknowingly passing the variant on to their children.

When a child inherits two mutated copies of ALMS1 – one from each parent – the disorder develops. For this to happen, both parents must be carriers. With every pregnancy, there is:

• a 25% chance the child will have Alström Syndrome,

• a 50% chance the child will be a carrier,

• and a 25% chance the child will neither be affected nor a carrier.