Table 1: The Differential Diagnosis of Delusional Infestations Infections
Drug-induced
Neurological
Ectoparasitic infections:
Prescribed medications:
Parkinson’s disease Alzheimer’s disease Diabetic neuropathy
Scabies ( Sarcoptes scabiei ) Follicle ( Demodex ) mites Animal and plant mites Body lice ( Pediculus humanus corporis ) Pubic lice ( Pthirus pubis )
Ciprofloxacin Corticosteroids
Morgellons disease (an unrecognized, self-diagnosed neuropsychological disorder characterized by delusional infestation) Trichotillomania (a compulsive urge to pull out and, in some cases, eat one’s own hair, usually on the scalp)
Phenelzine Topiramate
Cutaneous larva migrans:
Illicit drugs:
Cerebrovascular disease:
Animal hookworms ( Ancylostoma braziliensis ) Avian schistosomal cercarial dermatitis (swimmer’s itch or duck hunter’s itch)
Cocaine
Temporoparietal lobe infarcts
Miscellaneous infections:
Shingles (Herpes zoster) Hansen’s disease
cal care for intensely pruritic, erythematous, papular rashes that were subsequently determined to be caused bymultiple bites from European itch mites ( Peymotes herfsi ) (Figure 1). 9 These insect mites are ectoparasites of leaf-rolling fly larvae that fall from oak trees or get carried by the wind and land on people outdoors, causing summertime community out- breaks of pruritic rashes. 9 Another common cause of seasonal clusters of pruritic rashes may be caused by aquatic exposures to the infective stage cercariae of several avian schistosomes, or flatworms, that are released into freshwater lakes and rivers in the tens of thousands by infected aquatic snail intermediate hosts in a complicated life cycle (Figure 2). Cercarial dermatitis, or swimmer’s (duck hunter’s) itch, has occurred in seasonal outbreaks in swimmers in freshwater lakes and rivers whose resident or migratory waterfowl are infected with avian schistosomes (Figure 3). Lastly, several drugs; metabolic disorder-associated peripheral neuropathies, especially dia- betic neuropathy; and some neurodegenerative diseases, especially Parkinson’s and Alzheimer’s diseases; can cause dysesthesias with bug-crawling skin sensations that mimic arthropod infestations (Table 1). 1,2,10,11 Prior to the discovery of antipsychotic medications, Wil- son and Miller reported a poor prognosis for patients with delusional infestations with 82%of 51 reported patients hav- ing no change in their illnesses. 3 However, by the 1990s and with the use of the first generation or typical antipsychotics in managing delusional infestations, especially pimozide, Trabert reported nearly 70% improvement in patients with pharmacotherapy. 7,12 Today, the best management strategies for patients with delusional infestations include careful and empathetic work-
phenomenon (Case 2). 1, 2 In addition, Case 4 demonstrated a unique variation of delusional infestation, now known as Morgellons disease or syndrome, by producing “round worms” rolled in paper tissues. 6 Morgellons disease is defined as an unrecognized medical and/or neuropsychiatric disorder in which embed- ded fibers of cellulose or cotton fromclothing or paper can be demonstrated microscopically in self-excoriated, intensely pruritic and self-excoriated skin lesions in patients suffering from delusional infestations. 6 In 1995, Trabert reported the results of his comprehen- sive meta-analysis of 193 reports of delusional infestations over 100 years that included 1,123 case-patients. 7 The inci- dence in Germany was 1.6 cases per million cases per year with a mean age of case-patients of 57 years. 7 The ratio of female-to-male cases was 1.4:1.0 for those under age 50 years and 2.5:1.0 for those 50 years of age and older. 7 Subsequent descriptive and analytical epidemiological investigations, including our own small case series, have confirmed simi- lar demographic characteristics. 8 When Reilly and Batchlor surveyed 386 dermatologists in the United Kingdom, 66% reported seeing at least one patient with delusional infesta- tion within the past five years. 8 The major differential diagnoses of delusional infesta- tion include true ectoparasitic infections and cutaneous larva migrans, which must be ruled out initially by careful recreational, occupational, and travel histories, microscopic and laboratory tests, and drug-induced or neurological disease-associated dysesthesias (Table 1). Ectoparasitic in- fections, such as scabies and animal mite infestations, may occur in large seasonal clusters, such as in Pittsburg, Kansas, inAugust 2004, when 300 residents sought immediatemedi-
J La State Med Soc VOL 166 July/August 2014 157
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