Koebner Phenomenon Associated With Guttate Psoriasis

A 22-year-old white man presented to the clinic with a 2-month history of a pruritic rash consisting of papules and plaques over his trunk and upper extremities. He reported that the rash had appeared suddenly. He denied fever, nausea, weight loss, and malaise. His past medical history was unremarkable. He had received a tattoo on his right shoulder 2 weeks prior to the onset of the rash.

Physical examination. Multiple well-circumscribed plaques ranging in size from 1 mm to 1 cm were present on his chest, back, and arms (Figure 1). Also noted were erythematous papules outlining the tattoo on his right shoulder (Figure 2).

One week later, after conservative treatment, the lesions had progressed in size and severity (Figures 3 and 4).

Based on the clinical findings, the patient received a diagnosis of guttate psoriasis and associated Koebner phenomenon.

Discussion. Psoriasis is an inflammatory, hyperproliferative disorder of keratinocytes. Guttate psoriasis is an acute form that more commonly affects children and young adults.¹ Guttate psoriasis is characterized by multiple scaling papules and/or plaques with abrupt onset. The lesions generally range in size from a pinpoint to 1 cm. Initially the trunk and extremities are affected; as the condition progresses, the plaques enlarge, and the face and scalp may become involved. Pruritus is common.

Guttate psoriasis often presents after infection with group A streptococcus; therefore, throat cultures should be taken in suspected cases.¹ The etiology of guttate psoriasis is unknown, but strong evidence supports a genetic cause.²

The Koebner phenomenon is the appearance of lesions at the site of physical trauma such as sunburn, scratching, or as in this case, a tattoo.³ 

Diagnosis. The diagnosis of guttate psoriasis almost always is made clinically. Biopsy rarely is necessary. The differential diagnosis should include tinea, cutaneous lupus erythematosus, mycosis fungoides, and atopic dermatitis.

Treatment. Guttate psoriasis may resolve without treatment and, if asymptomatic, watchful waiting may be appropriate. The psychological toll of guttate psoriasis lesions must be considered. Topical treatment with calcipotriene, corticosteroids, and coal tar products should be tried first. Sunbathing often improves the disease. UV-B exposure and psoralen-UV-A therapy also may be used for generalized disease. Treatment with biologic agents such as etanercept, efalizumab, or adalimumab may be warranted.⁴ Systemic corticosteroids should not be used to treat guttate psoriasis, because their use may lead to pustular psoriasis.

Guttate psoriasis generally responds well to treatment and has a better prognosis than does plaque psoriasis, although guttate psoriasis may progress to plaque psoriasis.^1,4,5

References:

1. Habif TP. Psoriasis. In: Habif TP. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 5th ed. Philadelphia, PA: Mosby Elsevier; 2010:264-308.
2. Mahil SK, Capon F, Barker JN. Genetics of psoriasis. Dermatol Clin. 2015; 33(1):1-11.
3. Sagi L, Trau H. The Koebner phenomenon. Clin Dermatol. 2011;29(2):231-236.
4. Ferri FF. Psoriasis. In: Ferri FF. Ferri’s Clinical Advisor 2015. Philadelphia, PA: Mosby Elsevier; 2014:997-998.e.1.
5. Chalmers RJ, O’Sullivan T, Owen CM, Griffiths CE. Interventions for guttate psoriasis. Cochrane Database Syst Rev. 2000;(2):CD001213. doi:10.1002/14651858.CD001213.

Disclaimer: The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the US Navy Medical Corps or the US Department of Defense at large.