P.I.E (scientific name: Autism mortiferum) is a form of autism that doesn't really hurt much except social skills. Symptoms vary, except it generally makes people behave different from normal people.
It can also make sudden sicknesses start with no warning. One can spontaneously catch the flu, cold, or in rare cases deadly diseases, like Ebola or Rabies. P.I.E also feeds itself. It can develop more symptoms as you get older.