Delusional tinea: A novel subtype of delusional parasitosisDepartment of Dermatology, MD Anderson Cancer Center, University of Texas-Houston, Houston, Texas. firstname.lastname@example.org
Elizabeth RC Geddes MS, Rashid M Rashid MD PhD
Dermatology Online Journal 14 (12): 16
Delusions of parasitosis is one of the more complex management problems encountered in the dermatology clinic. The difficulty mainly arises from the fact that a psychiatric disease is responsible for the cutaneous pathology. Typically, patients complain of "parasites" or other crawling bugs on their skin. The delusion and its presentation are surprisingly consistent from patient to patient and effective management requires incorporation of psychiatric principles. In this report, we present a rare case of delusion in which the perpetrator was believed to be a "fungus."
The earliest account of Delusional Parasitosis documented in the medical literature was a case report in 1894 describing "les acarophobia,"  literally a "fear of mites." Since "phobia" implies a persistent, debilitating fear recognized as irrational by the affected individual, Ekbom  in 1938 pointed out the flawed terminology and suggested a new designation for psychogenic infections. In 1946 Wilson and Miller introduced the term "Delusion of parasitosis,"  which reflected the insistent nature of the patient's beliefs. As the term implies, parasites are the classically perceived offender. Here we present a novel case in which the delusion was the belief in the presence of persistent infection by a fungus.
A 49-year-old female presented with the complaint of fungal infection of one month duration. Initially her complaint was of intermittent itch with accompanying yellow-green change of nails and yellow flaky skin on her feet. Presently, the patient claims the fungus is on both arms, legs, and scalp, and continues to spread causing occasional itch during the daytime. The primary care physician prescribed topical butenafine, one percent, to which the patient complied for one week claiming no improvement of condition; she was subsequently referred to Dermatology. On physical examination, skin findings were unremarkable. She exhibited minimal excoriations and no nail or hair abnormalities. Scrapings for KOH preparation of her feet, hands, and scalp were negative. The patient then insisted the fungus is visible with a special "fungal light" used by the primary care physician. A Wood's Light was shown to the patient, and after she agreed it was identical, was used to examine the patient; it revealed no significant findings. The patient insisted on treatment and was given topical nafitin, one percent, and requested to return in one month. Over the following five days, she called our clinic and her PCP one to two times daily complaining about the fungus and was seen in follow-up with Dermatology on the fifth day. At that time, she complained that the fungus had spread to her floors, walls, dishes, and teeth. On this visit, the patient produced her own Wood's Light and demonstrated her own positive findings illustrating how her teeth would glow. The patient denied a psychiatric history but admits seeing a psychiatrist for smoking cessation. The illogical nature of the fungal infection was discussed at length and the patient appeared convinced of the psychogenic nature of her condition. The patient was referred to the Psychiatry department, but then later disagreed with the recommendation. The patient also notified us that she had obtained a referral to the Infectious Disease department. At present, she denies suicidal thoughts, homicidal thoughts, paranoia, hearing voices, or having hallucinations.
It has been estimated that for every seven years practicing, a dermatologist could expect to see one patient with Delusional Parasitosis . In patients younger than 50 years of age, the gender distribution is roughly equal; in patients over the age of 50, there is a female-to-male ratio of approximately 3:1 .
Delusional Parasitosis (DP) is considered to be a monosymptomatic hypochondriacal psychosis and falls under the category of Delusional Disorder-somatic type in the DSMIV-R. These patients present to primary care physicians or dermatologists with complaints of infestation by parasites. They bring in "specimens" to support their claim, classically referred to as "the matchbox sign." As with all delusionary notions, no amount of persuasion, reasoning, or evidence to the contrary can shake these patients of their fixed belief. This was certainly true in our case and the patient was not content with the advice of her family physician or dermatologist. She expressed a desire to seek out an Infectious Disease specialist for help.
When suspecting DP, one first needs to rule out true infestations or underlying cutaneous disease. The patient must also be evaluated for substance abuse; cocaine and amphetamine-induced formication is associated with "crawling" sensations and can thus mimic DP. Lastly, one must rule out systemic disorders . As this case shows, treating confirmed DP might be the most frustrating part of case management because the majority of patients reject a psychiatric referral. Once rapport is established, the physician should gently offer a trial of an antipsychotic agent with an emphasis placed on potential symptom reduction . Pimozide is traditionally the drug of choice.
Our case of delusional tinea illustrates a very rare form of delusion in which the sensory complaint is predominately visual, with some mild itch. Most patients with DP also experience formication or intense pruritus . It has been theorized that autosuggestion is responsible for visualization of the organisms, e.g. "I itch; therefore, I must have an infestation"  is the idea that leads one to imagine the creeping pests. However, with our case the hallucinatory component neither resulted from a tactile experience, nor did it stem from irritation or excoriations subsequent to attempted self-treatment. Our patient's delusion was deeply founded upon seeing the spreading "fungus" with the aid of a Wood's Lamp on white objects such as dishes, curtains, blankets, teeth, and lint. It is possible that her condition originated from a mistaken belief that any glowing indicates the presence of fungus, but the persistence and escalation of her symptoms despite considerable discussion with professionals highlights the delusionary nature. The novelty of our case resides in its bizarre presentation. Although delusional parasitosis is uncommon, delusions of a rampant fungal infection is extraordinarily rare. To our knowledge, only one other case of delusional tinea has been mentioned in the literature thus far . Although no formal imaging studies have been conducted to evaluate the disease process, magnetic resonance imaging of two cases revealed an abnormal striatum of the brain . This finding supports a proposed etiology of DP as being due to excess extracellular dopamine from a decrease in the function of striatal dopamine transporters .
Sadly, individuals affected by this disorder spend many angst-filled years searching for a medical professional to "treat" their perceived disease. Too often the physician's initial attempt is a quick referral to the next person in a line of specialties and that ultimately culminates with Psychiatry. However, even though patients often do not accept the diagnosis, early recognition of this entity and its subtypes could relieve some of the burden on the health care system and on the patient.
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