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INTRODUCTION TO CHAPTER

Psychiatric diseases are commonly associated with cutaneous pathology. Psychophysiologic skin disorders result from precipitation or exacerbation of skin disease by psychosocial stress.1 These are particularly common in acne, lupus erythematosus, psoriasis, telogen effluvium, and many other dermatologic diseases are well-known examples.1–3 This chapter will focus on primary psychiatric skin disorders, including delusional infestation, dermatitis artefacta, and obsessive compulsive disorders affecting the skin, where an underlying psychiatric disease results in self-induced cutaneous findings. In contrast, secondary psychiatric skin disorders describe primary skin diseases that result in stress, anxiety, or depression.

DELUSIONAL INFESTATION

Introduction

Delusional infestation describes the fixed, false belief of mucocutaneous infestation with parasites, particles, fibers, or other living or non-living material.4 Patients do not have other delusions, although comorbid psychiatric disease, such as anxiety, depression, or substance use, is common.5 The prevalence is approximately 80 per million in the outpatient setting.5 Delusions of parasitosis (delusional parasitosis) refers specifically to delusional infestation of living parasites, often arthropods or worms. Morgellons disease is a variant of delusional infestation attributed to inanimate fibers or particles.

Clinical Presentation

History and Physical Examination

Patients frequently note the sensation of crawling, biting, or stinging on the skin. Reported visualization of parasites, particles, or fibers is common, and many patients bring previously collected samples to their visit for clinical evaluation (specimen sign) (Figure 29-1). By definition, patients lack insight and are unable to accept alternative explanations for their symptoms. Excoriations from extraction attempts may result in erosions, ulcers, (Figure 29-2) prurigo nodularis, lichenification, hair loss, and secondary infection.

Figure 29-1.

Delusional parasitosis. Collection of cloth fibers, food particles, black seeds, dust and skin debris that patients interpret as being "bugs" (specimen sign).

Figure 29-2.

Delusional parasitosis. Numerous excoriations from extraction attempts are apparent, resulting in erosions and shallow ulcers.

Self-isolation and fear of contamination of family members or friends are common, but 8–12% present with folie à deux, shared delusions in a close contact.5 Many patients describe repeated courses of topical and systemic antiparasitic agents from past providers, repeated use of home exterminators, or frequent moves to attempt to escape recurrent infestation.

Laboratory Findings

No laboratory abnormalities are commonly observed.

Diagnosis

Diagnosis is based on characteristic clinical presentation and exclusion of other causes of symptoms. It is particularly important to rule out true infestation, as well as other potential underlying medical, metabolic, neurologic, substance abuse, or psychiatric disorders that may cause similar symptoms. Examination of the patient's entire body and clothing should ...

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