The history of schizotypal personality disorder (SPD) begins with the history of schizophrenia. Eugen Bleuler, in his initial description of schizophrenic illness, broadened Kraepelin's construct of dementia praecox to include what Bleuler termed latent schizophrenia, a less severe, non-psychotic presentation of schizophrenia. Empirical evidence that latent schizophrenia might share a common etiology with more severe schizophrenia was Bleuler's observation of a familial link between latent and chronic schizophrenia. Kretschmer published illustrative pedigrees demonstrating the occurrence of schizophrenia-like symptoms among the family members of schizophrenic individuals, and described in some detail the characteristics of what he called a schizoid temperament observed among some of the relatives of these patients. The body of family-genetic research in schizophrenia provides empirical evidence for the presence of a non-psychotic syndrome characterized by milder forms of the symptoms of chronic schizophrenia in some of the biological relatives of schizophrenic individuals.