Down Syndrome Disintegrative Disorder: A Clinical Regression Syndrome of Increasing Importance.

Down syndrome disintegrative disorder (DSDD), a developmental regression in children with Down syndrome (DS), is a clinical entity that is characterized by a loss of previously acquired adaptive, cognitive, and social functioning in persons with DS usually in adolescence to early adulthood. Initially reported in 1946 as "catatonic psychosis," there has been an increasing interest among the DS community, primary care, and subspecialty providers in this clinical area over the past decade. This condition has a subacute onset and can include symptoms of mood lability, decreased participation in activities of daily living, new-onset insomnia, social withdrawal, autistic-like regression, mutism, and catatonia. The acute phase is followed by a chronic phase in which baseline functioning may not return. No strict criteria or definitive testing is currently available to diagnose DSDD, although a comprehensive psychosocial and medical evaluation is warranted for individuals presenting with such symptoms. The etiology of DSDD is unknown, but in several hypotheses for regression in this population, psychological stress, primary psychiatric disease, and autoimmunity are proposed as potential causes of DSDD. Both psychiatric therapy and immunotherapies have been described as DSDD treatments, with both revealing potential benefit in limited cohorts. In this article, we review the current data regarding clinical phenotypes, differential diagnosis, neurodiagnostic workup, and potential therapeutic options for this unique, most disturbing, and infrequently reported disorder.