Abstract
PIDs are heterogeneous disorders caused by hereditary genetic defects of the immune system. The immune system normally helps the body fight off infections by germs/'micro-organisms' such as bacteria, viruses, fungi and protozoa. Because the immune systems do not work properly, people with PIDs are more prone than other people to infections. When PIDs are left undiagnosed or misdiagnosed, the immune system remains defective, often leading to illness, disability, permanent organ damage or even death. Too often infections are treated while missing the underlying cause. Current estimates of the prevalence are 1:1200 patients. Knowledge gaps, delayed diagnosis and treatment are leading into increased morbidity and mortality. Unlike many (rare) diseases, effective treatment options for PID patients are available, which can enable them to carry out a next to normal life. PID patients must therefore be diagnosed early and informed about the most adequate treatment for their particular condition. Unfortunately, none of the available therapies can reverse the damage of late diagnosis.