Congenital dermatoglyphic malformations and psychosis: A twin study

objective: In a previous twin study, congenital dermatoglyphic abnormalitie s, such as ridge dissociations and abnormalities of palmar flexion creases; were more prevalent in twins with psychotic and related disorders than in c omparison twins. This study was an attempt to replicate that finding in an independent study group. Method: Ridge dissociations and abnormal palmar flexion creases were assess ed in monozygotic pairs concordant (19 pairs) and discordant (31 pairs) for psychosis and related disorders. Results: The presence of either ridge dissociations or abnormal palmar flex ion creases was higher in the combined group of affected concordant and dis cordant twins (37.7%), than in the nonaffected discordant twins (20.0%; odd s ratio=2.4). In the discordant pairs, the presence of either abnormality w as strongly associated with psychotic disorder (odds ratio=3.0). Conclusions: Factors affecting early fetal development may increase the ris k for psychotic disorder. Differential exposure to such early risk factors may contribute to twin discordance for psychotic disorder.