You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Autoimmune diseases are common in both human and veterinary patients and they share some common characteristics and possibly common causes

Immune-mediated diseases in which damage is caused to the patients own organs are called "autoimmune" diseases. An official definition of autoimmunity is :

"Autoimmunity is reactivity of the immune system against self-antigens (autoantigens), that is the antigens expressed by normal constituent cells or proteins of the patient"

Some autoimmunity is normal physiological activity - for example old red blood cells express a new antigen on their surface which then stimulates an immune reaction to destroy them. It is only when the immune reaction abnormally damages tissues it is called an autoimmune disease, and these are common in both humans and veterinary patients. They are usually severe and debilitating - or even fatal. 

The precise aetiopathogenesis of autoimmune diseases is not fully understood, but it is now clear that they can occur as a consequence of exposure to infectious agents.

Factors that are thought to be important in the triggering of immune-mediated disease by an infection are :

• Genetic predisposition in the patient
• The infectious agent may have similar antigens to the patient (called antigenic mimicry)
• Inflammation in tissues may increase their sensitivity when exposed to immune cells/substances

The following table summarises some of the immune-mediated diseases in humans and dogs, and whether or not the disease is linked to exposure to an infectious agent (virus, bacteria or parasites) :

Updated January 2016