[Social Cognitive Impairment in Myotonic Dystrophy Type 1].

Myotonic dystrophy type 1 (DM 1) is a heritable, multisystem disease that affects not only the muscles but also the brain. DM 1 is often accompanied by developmental behavioral disorders, such as autism spectrum disorders. The autistic traits in DM 1 may be related to social cognitive dysfunction. The social cognitive function of patients with DM 1 was examined with respect to facial emotion recognition and theory of mind, which is the specific cognitive ability to understand the mental states of other people. With respect to facial emotion recognition, the sensitivities to disgust and anger were lower among patients with DM 1 than among healthy subjects, and this difference could not be attributed to visual impairment. To examine the theory of mind ability, the "Reading the Mind in the Eyes" test and the faux pas recognition test were used. Patients with DM 1 were found to be impaired in both tests, but the results were not attributed to visual ability and lexical comprehension. The possible causes of social cognitive dysfunction in DM 1 are the l cerebral atrophy and white matter abnormalities in the temporal, frontal, and insular cortex. Dysfunctions in these areas may affect the emotional and theory of mind abilities in DM 1, which result in the behavioral and communication disorders.