1. A form of infantilism (immaturity) that is a result of pituitary insufficiency, in which there is arrested growth (lack of physical development) but no deformities: Because of Joan's ateliosis, she had a very small body and her voice and face resembled those of a child even though she was over 50 years old.
2. Incomplete development which may refer to psychic infantilism or puerilism, and/or to physical dwarfism (microsomia): The unusual acting troupe consisted of people with atelioses; that is, they were dwarfish in stature but they were wonderful actors.