Successful Treatment of Delusional Infestation withOlanzapine Depot

Abstract

Delusional infestation (DI) is a rare psychiatric disorder characterized by a persistent falsebelief that one is infected with nonliving or living pathogens, usually accompanied byformication. Other psychotic features, such as disorganized speech or hallucinationsunrelated to the core delusion itself, are never present, and the delusional belief does notextend into other areas of life. Secondary DI, when one needs to address the underlyingcondition in order to achieve adequate treatment, is also possible. We present the caseof a 42-year-old male with a 2-year history of having a persistent and firm belief that hishouse was infested with tiny insects that were constantly biting him and laying their eggsunder his skin. His delusional belief was preceded by a complex, years-long substance usedisorder, which confronted us with a differential diagnostic dilemma between primaryand secondary DI. He was successfully treated with olanzapine pamoate depot, which wasintroduced to address his lack of insight and unsatisfactory compliance, and his delusionfaded away after his symptoms subsided.