Photo Quiz

An Itch That Must Be Scratched

Am Fam Physician. 2006 Jan 15;73(2):299-300.

A 42-year-old woman presented with pruritus of the face and back of five years’ duration. She denies concern for parasite or insect infestation. Linear excoriations in groups of two, three, and four were found on her back (see accompanying figure). Her face had several scattered, small, crusted lesions. Scalp hair was intact. Potassium hydroxide preparation was normal. No signs of insect or parasite infestation were found. Results of a complete blood count, endocrine work-up, mammography, chest radiography, hepatitis panel, and urinalysis were within normal limits. Antihistamines, antibiotics, and topical steroids were prescribed in the past without relief. The patient’s only long-term medication was paroxetine (Paxil) for depression.

Question

Based on the patient’s history and physical examination, which one of the following is the correct diagnosis?

A. Prurigo nodularis.

B. Lichen simplex chronicus.

C. Psychogenic excoriation.

D. Psychogenic parasitosis.

E. Trichotillomania.

Discussion

The answer is C: psychogenic excoriation. Although benign skin or nail picking is a simple habit, when it affects the patient emotionally or physically, it can be called psychogenic excoriation. Family physicians often are the first to see these patients, who may constitute up to 2 percent of dermatology clinic patients.1 Other names for psychogenic excoriation include dermatotillomania, compulsive skin picking, and neurotic excoriation.2 Psychogenic excoriation can be differentiated from dermatitis artefacta, in which patients deny scratching. Other compulsive skin disorders include trichotillomania, liplicking dermatitis, psychogenic parasitosis, lichen simplex chronicus, and prurigo nodularis. A characteristic sign of many of these disorders is scratching that occurs only in areas easily reached by the hand. As seen in the accompanying figure, areas where the patient cannot reach, such as the middle of the back, are unaffected.

Patients with psychogenic excoriation are usually women 20 to 50 years of age. Older patients tend to have more recalcitrant cases.2 Evaluation for other causes of pruritus includes ruling out cholestasis, hepatitis, thyroid abnormality, occult malignancy, and insect infestation.

Anxiety and mood disorders often are involved in the maintenance of behaviors and symptoms associated with psychogenic excoriation. In one study,3 59 percent of patients with psychogenic excoriation had a primary diagnosis of body dysmorphic disorder, impulse control disorder, or obsessive-compulsive disorder based on criteria from the Diagnostic and Statistical Manual of Mental Disorders, 4th ed. Most patients in the study excoriated without response to skin sensation, and a minority excoriated to pruritus. Patients with this disorder need to be taken seriously, reassured that the problem is genuine, and told they will be helped to gain control of their disorder.

Although high-quality evidence supporting the best treatment is limited, selective serotonin reuptake inhibitors are an appropriate initial choice.2,4 Some case reports5 describe success with olanzapine (Zyprexa). Mild cases can be treated with topical steroids, doxepin (Sinequan) at antipruritic doses, and empathic support. Sedative antihistamines can be prescribed at night when pruritus is most severe. Long-term cases may require behavior modification, which does not resolve the underlying cause but can produce temporary good results.

Prurigo nodularis typically displays discrete nodular plaques on the extremities that form from excessive skin picking. Lichen simplex chronicus is an eczematous reaction with lichenified plaques arising from repeated scratching of an area. Psychogenic parasitosis results from a fixated belief that one is infested with parasites or insects; patients pick at discrete areas in an effort to remove the imagined parasite. These three conditions tend to form in areas of the body that the patient can reach easily. Trichotillomania involves compulsive hair pulling, most often on the scalp.

Selected Differential Diagnosis of Self-perpetuated Skin Disorders

Condition Characteristics

Prurigo nodularis

Thickened nodules on the arms and legs

Lichen simplex chronicus

Lichenified skin plaques, most often in the lower leg and groin areas

Psychogenic excoriation

Linear excoriations on the arms, legs, upper back, and scalp

Psychogenic parasitosis

Discrete scars and excoriations on the face, legs, and arms; fixated belief in parasite or insect infestation

Trichotillomania

Repeated hair pulling; excoriation uncommon

Selected Differential Diagnosis of Self-perpetuated Skin Disorders

View Table

Selected Differential Diagnosis of Self-perpetuated Skin Disorders

Condition Characteristics

Prurigo nodularis

Thickened nodules on the arms and legs

Lichen simplex chronicus

Lichenified skin plaques, most often in the lower leg and groin areas

Psychogenic excoriation

Linear excoriations on the arms, legs, upper back, and scalp

Psychogenic parasitosis

Discrete scars and excoriations on the face, legs, and arms; fixated belief in parasite or insect infestation

Trichotillomania

Repeated hair pulling; excoriation uncommon

REFERENCES

1. Arnold LM, Auchenbach MB, McElroy SL. Psychogenic excoriation. CNS Drugs. 2001;15:351–9.

2. Koblenzer CS. Psychologic aspects of skin disease. In: Freedberg IM, Eisen AZ, Wolff K, et al., eds. Fitzpatrick’s Dermatology in general medicine. 5th ed. New York: McGraw Hill, 1999:475–86.

3. Arnold LM, McElroy SL, Mutasim DF, Dwight MM, Lamerson CL, Morris EM. Characteristics of 34 adults with psychogenic excoriation. J Clin Psychiatry. 1998;59:509–14.

4. Fried RG. Evaluation and treatment of “psychogenic” pruritus and selfexcoriation. J Am Acad Dermatol. 1994;30:993–6.

5. Blanch J, Grimalt F, Massana G, Navarro V. Efficacy of olanzapine in the treatment of psychogenic excoriation. Br J Derm. 2004;151:714–5.

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