While all autoimmune diseases will lead to a decreased life expectancy and can quickly affect the quality of life for each individual, the most dangerous and fatal autoimmune disorders include: - Autoimmune myocarditis: This condition is so dangerous because it is incredibly underdiagnosed, and directly affecting the cardiovascular health of the patient, increasing the risk of sudden death substantially when left untreated. - Multiple Sclerosis: This condition is has shown to drastically lower the quality of life and life expectancy of patients by causing permanent damage to the central nervous system, especially early on in the condition. - Lupus: The only real treatment for this condition is through immunosuppressants, which can substantially lower a patient’s ability to fight off any other diseases or infections, which often will end up being the cause of death for these patients. - Vasculitis: Severe cases can lead to increased damage to the organs and form blood clots, which can quickly become fatal. One of the reasons that autoimmune diseases are so serious and require close observation throughout the patient’s entire life is that most treatments result in a weakened immune system, making it impossible for the patient to effectively fight off other diseases and infections, some of which may be quite severe. Most of these conditions end up lowering the life expectancy of the patient by several years and come with a variety of symptoms that can affect day-to-day life.