Individuals with Asperger syndrome may, when exposed to hostility (e.g. bullying at school or at work), develop hostile ideas against their social environment, sometimes leading to aggression. These ideas and acts may be confounded with those arising from a persecutory state in schizoid or schizotypal personality, or even schizophrenia. These entities can be confounded with Asperger syndrome due to their permanent nature, and the presence of atypical social and emotional behaviours. This paper proposes cognitive (Wechsler profile), developmental (course of hostile behaviours), discursive (qualitative features of discourse reporting hostile thoughts), which may contribute to differential diagnosis in the presence of hostile thoughts and behaviours. Consequences for case management are also reported.