This is the DSM IV definition of Asperger's Syndrome, which has recently been folded into the Autism Spectrum Disorder. The old definition is a good analogue to a clinical description (if there was one) for a Xenos person.
DSM IV is significant because this was the last diagnostic tool to list “Asperger's Syndrome” before it was lumped in with “Autism Spectrum Disorder”. The distinctions and lives outside of disability were largely lost. A good starting explanation of Xenos is Asperger's that doesn't get to the level of debilitation.
Highlighted text is a reinterpretation of DSM IV that seems to fit Xenos more accurately.
A. [asocial - WeDoNotDoConferences, please] Qualitative impairment in social interaction, as manifested by at least two of the following:
B. [obsession - deep explorers and observers] Restricted repetitive and stereotyped patterns of behavior, interests, and activities, as manifested by at least one of the following:
C. The disturbance causes clinically significant impairment in social, occupational, or other important areas of functioning [ This is the difference between Xenos (no significant impairment in these) and Autism (Xenos with clinically significant impairment for these and the rest) ]
D. There is no clinically significant general delay in language (e.g., single words used by age 2 years, communicative phrases used by age 3 years).
E. There is no clinically significant delay in cognitive development or in the development of age-appropriate self-help skills, adaptive behavior (other than social interaction), and curiosity about the environment in childhood.