Activated PI3K-delta syndrome (also known as APDS) is a disorder that impairs the immune system. Individuals with this condition often have low numbers of white blood cells (lymphopenia), particularly B cells and T cells. Normally, these cells recognize and attack foreign invaders, such as viruses and bacteria, to prevent infection. The severity of activated PI3K-delta syndrome varies widely. Some people may have multiple, severe infections while others show mild symptoms to none at all.

Activated PI3K-delta syndrome is caused by variants (also called mutations) in the PIK3CD gene and the PIK3R1 gene. Activated PI3K-delta syndrome type 1 is caused by variants in the PIK3CD gene, which provides instructions for making a protein called p110 delta (p110δ). Activated PI3K-delta syndrome type 2 is caused by variants in the PIK3R1 gene. This gene provides instructions for making slightly different versions of another protein; the most common version is called p85 alpha (p85α).

Activated PI3K-delta syndrome is considered a rare disorder, but its exact prevalence is unknown.

Activated PI3K-delta syndrome is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

Published Date: August 16, 2023
Published By: National Institutes of Health