Immune disorder

An immune disorder is a dysfunction of the immune system. These disorders can be characterized in several different ways:
According to the International Union of Immunological Societies, more than 150 primary immunodeficiency diseases (PIDs) have been characterized. However, the number of acquired immunodeficiencies exceeds the number of PIDs.
It has been suggested that most people have at least one primary immunodeficiency. Due to redundancies in the immune system, though, many of these are never detected.
Autoimmune diseases.
An autoimmune disease is a condition arising from an abnormal immune response to a normal body part. There are at least 80 types of autoimmune diseases. Nearly any body part can be involved. Common symptoms include low-grade fever and feeling tired. Often symptoms come and go.
Immunodeficiencies.
Primary immune deficiency diseases are those caused by inherited genetic mutations. Secondary or acquired immune deficiencies are caused by something outside the body such as a virus or immune suppressing drugs.
Primary immune diseases are at risk to an increased susceptibility to, and often recurrent ear infections, pneumonia, bronchitis, sinusitis or skin infections. Immunodeficient patients may less frequently develop abscesses of their internal organs, autoimmune or rheumatologic and gastrointestinal problems.
Allergies.
An allergy is an abnormal immune reaction to a harmless antigen.