Photo Quiz

Erythematous, Scaly After Sun Exposure RITA S. MATOS, MD, Unidade de Saúde Familiar São Bento – Agrupamento de Centros de Saúde de Gondomar, Portugal TIAGO TORRES, MD, PhD, Centro Hospitalar Universitário do Porto; Instituto de Ciências Biomédicas Abel Salazar, University of Porto, Portugal

The editors of AFP wel- come submissions for Photo Quiz. Guidelines for preparing and sub- mitting a Photo Quiz manuscript can be found in the Authors’ Guide at http://www.aafp.org/ afp/photoquizinfo. To be considered for publication, submissions must meet these guidelines. E-mail submissions to afpphoto@ aafp.org. This series is coordinated by John E. Delzell Jr., MD, MSPH, Assistant Medical Editor. A collection of Photo Quiz published in AFP is avail- Figure 1. able at http://www.aafp. org/afp/photoquiz. Previously published Photo A 45-year-old woman presented with a Question Quizzes are now featured 10-day history of an erythematous, scaly rash Based on the patient’s history and physical in a mobile app. Get more information at http:// on her back that developed after a period of examination findings, which one of the fol- www.aafp.org/afp/apps. intense sun exposure. She did not have a lowing is the most likely diagnosis? or chills, and there was no discharge from the ❏ A. Herpes zoster. site. The patient was otherwise healthy. She ❏ B. Irritant contact . had a history of small, erythematous, scaly ❏ C. Koebner phenomenon. lesions on both elbows during adolescence ❏ D. rosea. that spontaneously resolved. Her family his- ❏ E. . tory was significant for maternal . Physical examination revealed multiple See the following page for discussion. erythematous, scaly plaques on the lower back just above the waistline (Figure 1). These lesions were in the area of sun expo- sure. There were no other lesions or physical findings.

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Discussion Irritant is skin inflam- The answer is C: Koebner phenomenon. mation typically after exposure to an irri- Koebner phenomenon is an isomorphous tant. It presents as , mild , rash that is commonly associated with pso- and scaling in the pattern of the exposure. riasis and other skin diseases such as The rash is a nonspecific response to direct and .1 It occurs following local irritant damage that releases inflammatory trauma in areas that are not involved with mediators.7,8 skin disease.2 The rash appears as clearly Pityriasis rosea is a common skin disorder defined, erythematous, scaly plaques.3 Pro- that occurs in otherwise healthy persons, voking factors can include physical trauma, most often children and young adults. The friction, surgical incision, burns, and radia- rash is a papulosquamous eruption that tion exposure.4 Koebner phenomenon lasts six to eight weeks. It typically begins appears to be unrelated to the activity or with a single salmon-colored herald patch severity of the associated skin disease.5 on the trunk, followed by multiple lesions In general, the Koebner phenomenon rash in a Christmas tree pattern. In some cases, appears 10 to 20 days after the local trauma.3 it appears to occur after upper respiratory The reported incidence varies widely from tract infection.7,8 5% to 75%.5 No definitive pathogenic pro- Tinea corporis is a superficial dermato- cess has been identified.6 In this patient, phyte infection characterized by an ery- the radiation from extensive thematous, scaly plaque with a raised, sun exposure appears to be the trigger. well-defined, advancing border. Following Pathogenic immunologic processes may central resolution, the lesion appears annu- be enhanced by ultraviolet radiation. The lar in shape.7,8 patient’s history of undiagnosed psoriasis Address correspondence to Rita S. Matos, MD, at may support this hypothesis. [email protected]. Reprints are not available from Herpes zoster is a painful rash caused by the authors. reactivation of the varicella . It usually Author disclosure: No relevant financial affiliations. begins with a prodromal phase character- ized by pain, itching, , or dyses- REFERENCES thesias in one dermatome. A few days later, 1. Gupta S. Many faces of Koebner phenomenon in pso- a unilateral maculopapular rash appears on riasis. Indian J Dermatol Venereol Leprol. 2002;​68(4):​ the affected area, which then evolves into 222-224. clusters of small, tender vesicles and 2. Bergboer JG, Oostveen AM, de Jager ME, et al. Koe- 7,8 bner phenomenon in psoriasis is not associated with in the corresponding dermatome. deletion of late cornified envelope genes LCE3B and LCE3C. J Invest Dermatol. 2012;132(2):​ ​475-476. 3. Alolabi N, White CP, Cin AD. The Koebner phenom- enon and breast reconstruction:​ psoriasis eruption Summary Table along the surgical incision. Can J Plast Surg. 2011;​19(4):​ 143-144. Condition Characteristics of the rash 4. Arias-Santiago S, Espiñeira-Carmona MJ, Aneiros- Fernández J. The Koebner phenomenon: ​psoriasis in Herpes zoster Clusters of small, tender vesicles and blisters tattoos. CMAJ. 2013;​185(7):​585. Irritant contact Erythema, mild edema, and scaling in the pattern 5. Camargo CM, Brotas AM, Ramos-e-Silva M, Carneiro S. dermatitis of the irritant exposure Isomorphic phenomenon of Koebner:​ facts and contro- versies. Clin Dermatol. 2013;31(6):​ ​741-749. Koebner Clearly defined erythematous, scaly plaques 6. Raychaudhuri SP, Jiang WY, Raychaudhuri SK. Revisiting phenomenon following local trauma the Koebner phenomenon: ​role of NGF and its receptor Pityriasis rosea Single salmon-colored herald patch on the trunk, system in the pathogenesis of psoriasis. Am J Pathol. followed by multiple lesions in a Christmas tree 2008;​172(4):961-971​ . pattern 7. Habif TP, ed. Clinical :​ A Color Guide to Tinea corporis Annular, scaly plaque with a raised, well-defined, Diagnosis and Therapy. 5th ed. Edinburgh, Scotland: ​ Mosby;​ 2010. advancing border 8. Weller RP, Hunter HJ, Mann MW, eds. Clinical Derma- tology. Hoboken, N.Y.: ​Wiley Blackwell; ​2016. ■

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