In 17q21.31 microdeletion syndrome, hypersocial behaviour may be part of the neuropsychological phenotype

Abstract

Objective: The 17q21.31 microdeletion encompasses among others the microtubule associated protein tau (MAPT) gene that is highly expressed in the brain and is involved in several neurodegenerative disorders such as fronto-temporal dementias and progressive supranuclear palsy. It can be postulated that in 17q21.31 microdeletion syndrome (17qMDS), normal brain development is disturbed as a result of MAPT haploinsufficiency, which in turn may compromise neurocognitive functioning. It is hypothesized that hypersocial behaviour, which has been observed in these patients, results from impaired response inhibition subsequent to prefrontal lobe dysfunction. Participants and Methods: The present study aims to investigate neurocognitive functioning, including measurement of personal space (PS) and sensitivity for fairness (DG), in three patients with a genetically proven 17qMDS and in three intellectually disabled, physically healthy control subjects. Results: All subjects, patients and controls, were moderately intellectually disabled with a congruent cognitive profile, except for a relatively strong memory for social-contextual information in the patients. As to social cognition, in both patients and controls, mentalizing abilities were confined to simple perspective taking whereas basic facial emotion perception was undisturbed. In the control subjects, however, marked difficulties in the recognition and expression of experienced emotions (cf., alexithymia) were present. As reflected in the PS distance measures, patients generally tended to tolerate close proximity towards the investigator. However, they showed less generosity or fairness on the DG. Conclusions: Despite the methodological limitations characteristic for research in people with intellectual disabilities, with a neuropsychological assessment strategy, in three patients with 17q21.31 microdeletion syndrome, preliminary evidence for hypersocial behavior with a high level of frustration tolerance was found that may be implicated in its behavioral phenotype.