PIK3CD is a gene that provides instructions for making a protein involved in the phosphoinositide 3-kinase (PI3K) signaling pathway. This pathway plays a crucial role in various cellular functions, including growth, survival, and metabolism. The protein produced by PIK3CD is particularly important for the function of immune cells, helping them respond effectively to infections and other challenges. Mutations in the PIK3CD gene can lead to immune system disorders, such as hyper-IgE syndrome and combined immunodeficiency. These conditions can result in increased susceptibility to infections and other health issues. Understanding PIK3CD is essential for developing targeted therapies for related diseases.