Primary immunodeficiency diseases

Primary immunodeficiency diseases (PIDs) are a group of disorders with defects in the development or function (or both) of the immune system. Most PIDs originate from mutations in single genes, but polygenic forms do occur. The global prevalence of PIDs varies between 0.3 and 12 per 100 000 population, and is higher in areas with high rates of consanguinity. The prevalence in South Africa is unknown, but according to prevalence data reported from the PID register, these diseases are either missed or not reported. The possible reasons for under-diagnosis are that patients presenting with recurrent, persistent, severe or even unusual infections are treated without investigating the underlying cause, or the diagnosis is missed in the face of the overwhelming burden of similar clinical presentations of infectious diseases such as HIV and tuberculosis.