[One possible classification of the delusional misidentification syndromes and its developmental, regressive understandings].

In recent years, misidentification syndromes have attracted much attention, and various types of these syndromes have been recognized. However, misidentification syndromes tend to be discussed as case reports or as a whole, and yet there is no established classification. This is primarily due to a small number of cases encountered by each researcher. We propose a new classification of misidentification syndrome based on more than 70 patients with these syndromes, who have been treated at one psychiatric hospital during 20 years. First, delusional misidentification syndromes were classified into two types: misidentification of human relationships represented by descent delusion (relational misidentification), and misidentification of identity itself represented by Capgras symptom and Fregoli symptom (identical misidentification). Next, identical misidentification was subclassified into 3 types: division of identity (divided type), union of identity (unionized type), and transformation of identity (transformed type). Various misidentification syndromes and associated signs and symptoms were evaluated in detail from the aspect of descriptive psychiatry and were compared with our new classification. In addition, this typological study on misidentification was analyzed based on the regressive theory and Jacksonism, and we proposed a hypothesis that there is correspondence between misidentification syndromes and the development of person identification in infants.