"Doctor, You Must Examine My Creature Collection!": A Case Report of Delusional Infestation.

Delusional infestation--either secondary when attributed to a medical condition (including a bon-a-fide parasite infestation) or a pharmacologic agent (prescribed or illicit) or primary when secondary etiologies have been excluded--is a psychosis in which, for at least one month duration, the patient not only has a delusion that an animate organism or an inanimate pathogen has infested them, but also has abnormal tactile sensation (such as pruritus) of their skin caused by the etiology of their delusion. In patients over the age of 50 years, a delusional infestation is three times more common in women than men; however, delusional infestation in younger patients is often secondary, associated with illicit drug exposure, and equally common in women and men. Primary skin lesions are typically absent in delusional infestation patients; however, secondary skin lesions--resulting from the patient's efforts to remove the parasite from their skin--can be observed, such as excoriations, prurigo nodules, scars, and ulcers. Delusional infestation patients typically strive to convince the person evaluating them that their infestation is valid and many of these individuals do this by collecting the parasites in a container. Presentation of the pathogen-filled containers is a pathognomonic feature of delusional infestation that has been referred to as either a positive creature collection sign, match box sign, parasite preservation sign, pillbox sign, or specimen sign. Morgellons disease--in which the pathogen being extruded from the skin is a fiber--has several features (including an excellent response to treatment with antipsychotic agents) in common with delusional infestation; therefore, most investigators consider Morgellons disease to be a variant of delusional infestation. Delusional infestation can be associated with numerous diseases, including comorbid psychiatric conditions. Indeed, up to 15 percent of delusional infestation patients have one (folie a deux) or more individuals with similar symptoms. A man with delusional infestation is described who had a positive creature collection sign, a fixed belief that his symptoms were caused by the infesting organism, and refusal to accept that he had a psychiatric disorder. He insisted that the evaluating dermatologist examine the pathogens in the clear plastic container he brought with him to his appointment. He was convinced that the pruritus of his scalp, eyebrows, and eyelashes was associated with a non-existent lice infestation. Secondary delusional infestation was excluded and his concurrent mild seborrheic dermatitis was treated topically; however, his itching did not resolve. He eventually agreed to seek treatment with a psychiatrist. The management of delusional infestation is based on its etiology; resolving the underlying medical condition or discontinuing the causative pharmacologic agent is the treatment approach for secondary delusional infestation, whereas low-dose antipsychotic agents are the intervention of choice for treating primary delusional infestation.