The cause is unknown, it is noteworthy the contact with infectious agents bacterial and viral, among them, enteroviruses, herpes or the mumps virus, but no specific isolation. Genetic predisposition is also considered, with the presence of an antigen of histocompatibility (HLA), in which a larger number of cases is observed in the same family.
In addition, environmental factors may also be considered for the emergence of the disease, by changing the endocrine system and influence on the homeostasis of the immune system, such as for example the exposure to trauma stress-both physical and emotional.