Delusional parasitosis

Delusional infestation is classified as a delusional disorder of the somatic subtype in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). The name delusional parasitosis has been the most common since 2015, but the condition has also been called delusional infestation, delusory parasitosis, delusional ectoparasitosis, psychogenic parasitosis, Ekbom syndrome, dermatophobia, parasitophobia, formication and "cocaine bugs". Morgellons is a constellation of symptoms considered a form of delusional parasitosis in which people have painful skin sensations that they believe contain fibers of various kinds; its presentation is very similar to other delusional infestations, but people with this self-diagnosed condition also believe that strings or fibers are present in their skin lesions. ==Signs and symptoms==

People with delusional parasitosis believe that "parasites, worms, mites, bacteria, fungus" or similar organisms have infected them. Reasoning or logic cannot change this fixed, false belief. People with this condition may injure themselves by using harsh chemicals or cleaning obsessively or by trying to remove the "parasites", leading to skin damage such as excoriation, bruises, and cuts. A "preceding event such as a bug bite, travel, sharing clothes, or contact with an infected person" is often identified by individuals with DP; such events may lead the individual to misattribute symptoms because of more awareness of symptoms they were previously able to ignore. Nearly any marking upon the skin, or small object or particle found on the person or their clothing, can be interpreted as evidence for the parasitic infestation, and individuals with the condition commonly compulsively gather such "evidence" to present to medical professionals. This presentation is known as the "matchbox sign", "Ziploc bag sign" or "specimen sign", because the "evidence" is frequently presented in a small container, such as a matchbox. The matchbox sign is present in five to eight out of every ten people with DP. Related is a "digital specimen sign", in which individuals bring collections of photographs to document their condition. Similar delusions may be present in close relatives—a shared condition known as a folie à deux—that occurs in 5–15% of cases and is considered a shared psychotic disorder. Because the internet and the media contribute to furthering shared delusions, DP has also been called folie à Internet; when affected people are isolated from each other, their symptoms usually improve, but most still need treatment. Approximately eight out of ten individuals with DP have co-occurring conditions—mainly depression, followed by substance abuse and anxiety. Their personal and professional lives are often disrupted due to extreme distress over their symptoms. In primary DP, the delusions are the only manifestation of a psychiatric disorder. Secondary DP occurs when another psychiatric condition, medical illness or substance (prescription or recreational) use causes the symptoms. == Cause ==

The cause of delusional parasitosis is unknown as of 2019. Medical conditions associated with secondary delusional parasitosis include: deficiencies in vitamins such as B12 or folate, thyroid dysfunction, diabetes, Parkinson's disease, dementia, encephalitis, meningitis, and multiple sclerosis. Some infectious diseases such as HIV and syphilis have also been associated with DP. Secondary DP is also associated with substance use disorders—most commonly chronic alcohol use, alcohol withdrawal, long-term cocaine use, and long-term amphetamine use. A number of prescription drugs may cause DP as a side effect, including "phenelzine, pargyline, ketoconazole, corticosteroids, amantadine, ciprofloxacin, pegylated interferon alpha, and topiramate." ==Diagnosis==

Delusional parasitosis may be diagnosed when: 1) the delusion is the only symptom of psychosis, 2) the delusion has lasted a month or longer, 3) the person's behavior is otherwise not markedly odd or impaired, 4) mood disorders (if present at any time) have been comparatively brief, and 5) the delusion cannot be better explained by another medical condition, mental disorder, or the effects of a substance. For diagnosis, the individual must attribute abnormal skin sensations to the belief that they have an infestation, and be convinced that they have an infestation even when evidence shows they do not. Other related psychiatric conditions to be ruled out include schizophrenia, anxiety disorders, obsessive–compulsive disorder, dementia, delirium, affective or substance-induced psychoses, and medical conditions that cause psychosis. Several drugs, legal or illegal, such as amphetamines, dopamine agonists, opioids, and cocaine may also cause the skin sensations reported. Diseases that must be ruled out in differential diagnosis include hypothyroidism, and kidney or liver disease. ==Treatment==

People with DP often reject the professional medical diagnosis, and few willingly undergo treatment, despite demonstrable efficacy, making the condition difficult to manage. Reassuring the individual with DP that there is no evidence of infestation is usually ineffective, as that information is rejected. A five-phase approach to treatment is outlined by Heller et al. (2013) that seeks to establish rapport and trust between physician and patient. Dermatologists may have more success introducing the use of medication as a way to alleviate the distress of itching. Low doses of antipsychotic medication are used; A 2022 literature review found in a small sample of individuals who had comorbid conditions along with DP that most treated with SSRI antidepressants experienced remission of their DP symptoms. == Prognosis ==

People will often have symptoms for months before being diagnosed. The average duration of the condition is about three years. Cure may be achieved with antipsychotics or by treating underlying psychiatric conditions. DP drastically impacts the lives of those affected and can lead to social isolation which can worsen depressive symptoms. Depression and suicide risk is elevated in people affected by DP. The condition can also impact the ability to function in daily life and negatively impact employment. ==Epidemiology==

While DP is a rare disorder, it is the most common form of somatic delusion. The majority of dermatologists will see at least one person with DP during their career. About 56% of those with DP have primary DP. ==History==

George Thibierge, a French physician, coined the term acarophobia in the 1890s to describe individuals "with the devastating, unshakeable belief that they were infested with mites", according to Mendelsohn et al (2024). The eponymous Ekbom's disease was changed to "delusions of parasitosis" in 1946 in the English literature, when researchers J Wilson and H Miller described a series of cases, and to "delusional infestation" in 2009. The most common name since 2015 has been "delusional parasitosis". Morgellons Mary Leitao, the founder of the Morgellons Research Foundation, coined the name Morgellons in 2002, reviving it from a letter written by a physician in the mid-1600s. Leitao and others involved in her foundation (who self-identified as having Morgellons) successfully lobbied members of the U.S. Congress and the U.S. Centers for Disease Control and Prevention (CDC) to investigate the condition in 2006. The CDC published the results of its multi-year study in January 2012. The study found no underlying infectious condition and few disease organisms were present in people with Morgellons; the fibers found were likely cotton, and the condition was "similar to more commonly recognized conditions such as delusional infestation". Since the early 2000s, a strong internet presence has led to increasing self-diagnosis of Morgellons. An active online community has supported the notion that Morgellons is an infectious disease, and propose an association with Lyme disease. Publications "largely from a single group of investigators" describe findings of spirochetes, keratin and collagen in skin samples of a small number of individuals; these findings are contradicted by the much larger studies conducted by the CDC. == Society and culture ==

Jay Traver (1894–1974), a University of Massachusetts entomologist, has been characterized after her death as having made "one of the most remarkable mistakes ever published in a scientific entomological journal", after publishing a 1951 account of what she called a mite infestation. Her detailed description of her own experience with mites was later shown to be incorrect, Matan Shelomi says the paper has done "permanent and lasting damage" to people with delusional parasitosis, "who widely circulate and cite articles such as Traver's and other pseudoscientific or false reports" via the internet, making treatment and cure more difficult. == See also ==