Quiz

What is causing this pruritic lesion?

DAVID L KAPLAN, MD—Series Editor

Volume 44 - Issue 11 - November 2004
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Case 1: A 20-year-old woman presents with a 3-week history of a pruritic, progressively enlarging erythematous lesion on one arm. She has a cat and recently started horseback riding lessons. She is otherwise healthy and takes no medication.
             
Which of the following is the most likely cause of the lesion?
A. Granuloma annulare.
B. Bacterial cellulitis.
C. Brown recluse spider bite.
D.Tinea corporis.
E. Panniculitis.
 
What is the most appropriate diagnostic option?
F. Bacterial culture.
G. Fungal culture.
H. Biopsy.
I. Complete blood cell count and liver function tests.
J. Potassium hydroxide (KOH) examination. 
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Case 1: A KOH examination, J, confirmed the diagnosis of tinea corporis, D, that was most likely acquired from horseback riding. Zoophilic organisms are more likely than geophilic organisms to produce inflammatory, pruritic reactions. Granuloma annulare is asymptomatic. Bacterial cellulitis, brown recluse spider bite, and panniculitis are painful rather than pruritic. The patient responded quickly to antifungal therapy. A veterinarian was consulted about the horse.

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Case 2: The mother of a 2-year-old boy reports that he has had an asymptomatic yellowish nodule on his nose for the past 8 months. He is otherwise healthy and has no history of injury.

                     

Which of the following do you suspect?
A. Intradermal nevus.
B. Fibrous papule of the nose.
C. Spitz nevus.
D. Juvenile xanthogranuloma.
E. Urticaria pigmentosa.

Case 2: A biopsy confirmed the diagnosis of juvenile xanthogranuloma, D. This lesion, which is typically solitary, usually erupts in the first year of life; it is most commonly seen in white boys. Most lesions spontaneously involute within 5 years. If multiple lesions occur before the age of 2 years, an ocular examination is warranted, because 0.4% of patients will have intraocular lesions. Intradermal nevi usually do not have a yellowish tinge, and fibrous papules of the nose are not seen in this age group. Spitz nevi may resemble juvenile xanthogranuloma; the diagnosis is established on biopsy. Urticaria pigmentosa lesions become hive-like when they are stroked.
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Case 3: For 5 weeks, a 65-year-old woman has had an asymptomatic, erythematous, slightly elevated papule on her right temple. There is no history of trauma. She takes several medications for mild hypertension and osteoporosis, but no new medications have been added in the past 6 months.
                       

What does this lesion look like to you?
A. Actinic keratosis.
B. Lichenoid keratosis.
C. Seborrheic keratosis.
D. Fixed drug eruption.
E. Basal cell carcinoma.

Case 3: The patient had a lichenoid keratosis, B. This lesion has features of an actinic keratosis with a lymphocytic infiltrate. A biopsy is sometimes necessary to distinguish lichenoid keratosis from other lesions. Typically seen after midlife on sun-exposed areas, these lesions are treated with cryosurgery. Actinic keratoses and basal cell carcinomas do not typically enlarge so quickly; seborrheic keratoses are not usually inflamed. The patient’s history did not implicate drugs (although over-the-counter products can cause eruptions and should be included in the differential).