When a client enters therapy with a prior diagnosis, it might be difficult for the therapist to think outside of the box presented. One reason a dissociative individual might have several different diagnoses, however, is that as different parts present, they may also be presenting with diagnostic issues that are different from the host. Such differences especially make sense given the nature of DID.
Deborah Bray Haddock, The Dissociative Identity Disorder Sourcebook
dissociation, dissociative, dissociative-identity-disorder, mental-health, misdiagnosis, multiple-personality-disorder