Combined immunodeficiency due to ZAP70 deficiency is a rare, inherited disorder that affects the immune system. It is caused by mutations in the ZAP70 gene, which provides instructions for making a protein called ZAP70. This protein is important for the development and function of certain white blood cells, which are the body’s main defense against infection. People with this disorder have a weakened immune system, which makes them more susceptible to infections. Symptoms may include recurrent infections, failure to thrive, and skin rashes. Treatment typically involves antibiotics, immunoglobulin therapy, and bone marrow transplantation.