Letters

Molluscum Contagiosum–Induced advancing borders were found on the bilateral upper thighs Annulare Centrifugum and left inguinal area (Figure 1A). In the center of each Erythema annulare centrifugum (EAC), whether as a dis- plaque, there was a single 2-mm reddish-brown shiny pap- tinctive entity or a reaction pattern, manifests characteristic ule (Figure 1B). In addition, some smooth, shiny, pearly, and clinical and histopathologic features. It has been associated firm without peripheral erythema were also with infectious agents, particularly , other observed on the right lower abdomen and the bilateral pos- fungi (eg, Candida species, Penicillium species), bacteria (eg, terior thighs. He reported that these lesions were sometimes Mycobacteria species, species, Escherichia itching and sometimes painful. coli), viruses (eg, poxvirus, Epstein-Barr virus, varicella- A skin biopsy specimen was obtained from the central zoster virus, human immunodeficiency virus), and para- on the right upper thigh. Histopathologic examina- sites. Less commonly, EAC has been linked to drugs, tion showed lobulated, endophytic epidermal hyperplasia, connective-tissue disease, sarcoidosis, hypereosinophilic with a very large eosinophilic intracytoplasmic inclusion in syndrome, and pregnancy. However, many of these associa- each (Figure 2A). These features demonstrated tions are likely coincidental, and in most cases, no underly- . Heavy superficial perivascular ing cause is identified. Herein, we report a case of EAC lymphohistiocytic infiltrates, focal basal vacuolization, mild caused by molluscum contagiosum. spongiosis, and mounts of parakeratosis were also observed around the main lesion (Figure 2B). These peripheral find- Report of a Case | A 45-year-old man, in relatively good health, ings were compatible with the histopathologic features of presented with several gradually enlarging plaques on the superficial EAC. bilateral upper thighs of 1 month’s duration. On physical exanimation, several annular plaques, 0.5 to 5.0 cm in Discussion | Molluscum contagiosum is a common epidermal in- diameter, with raised edges and trailing scales behind fection caused by a poxvirus of the Molluscipox virus genus.

Figure 1. Molluscum Papules With Peripheral EAC-Like Reaction

A General clinical presentation B Lesion close-up image

EAC indicates erythema annulare centrifugum. A, Several 0.5- to 5-cm annular plaques on the bilateral upper thighs and left inguinal area. B, Close-up view of a lesion in the left inguinal area. Annular erythema is seen with trailing scale behind the advancing erythematous edge and central reddish-brown shiny papules.

Figure 2. Histopathologic Findings of a Skin Biopsy Specimen From a Central Papule on the Right Upper Thigh

A Original magnification x 100 B Original magnification x 200

Hematoxylin-eosin staining reveals typical features of molluscum contagiosum (A) and superficial perivascular lymphohistiocytic infiltrates, focal basal vacuolization, mild spongiosis, and mounts of parakeratosis around the molluscum papule (B).

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Approximately 10% of patients develop an eczematous reac- 6. Furue M, Akasu R, Ohtake N, Tamaki K. Erythema annulare centrifugum tion around the central molluscum papules.1 Other unusual re- induced by molluscum contagiosum. Br J Dermatol. 1993;129(5):646-647. active processes associated with molluscum infestation in- clude ,2 erythema multiforme,3,4 and erythema An Unusual 2-Tone Epidermal Cyst: annulare centrifugum.5,6 Erythema annulare centrifugum as- Dermoscopy, Confocal Microscopy, sociated with molluscum contagiosum was first described by and Histopathologic Correlations Vasily and Bhatia5 in 1978. To our knowledge, there are only 2 Noninvasive techniques such as dermoscopy and reflectant reports of this phenomenon in the literature. Based on the char- confocal microscopy (RCM) may enhance the diagnosis in some acteristic finding of annular erythema with trailing scale be- unusual nodules, as illustrated by the present case. hind the advancing erythematous edge and compatibility of the histopathologic findings in our case, we diagnosed mol- Report of a Case | A woman in her 30s reported changes in the luscum contagiosum–induced EAC. All lesions resolved within last 6 months to an originally asymptomatic nodule on her right 2 weeks after cryotherapy for molluscum papules and topical thigh. The 2-tone lesion of about 0.5 × 1 cm appeared to be exo- treatment with fluocinonide, 0.05%, cream for peripheral phytic and well demarcated: half of the lesion appeared whit- erythema. ish, and the other half was black (Figure 1A). Polarized-light The pathogenesis of molluscum contagiosum–associ- dermoscopy (DermLite hybrid; 3Gen) showed the presence of ated reactions remains obscure. One hypothesis has pro- 2 well-defined areas; one of them had a homogeneous yellow- posed that rupture and discharge of molluscum bodies into ish color, the other was irregularly bluish. Within the bluish the surrounding dermis elicits an immunologic reaction area, a circular, keratin-filled pore was observed (Figure 1B). that clinically presents as dermatitis surrounding inflamed Analysis by RCM, performed with the handheld VivaScope molluscum papules.3 In our case, EAC-like reaction was 3000 (Mavig GmbH), showed beyond the pore a keratin-filled mainly confined to the lesions on intertriginous areas and duct extending below the . In addition, just beneath the right lateral thigh, which were prone to friction, result- a thinned epidermis, highly reflectant, geometrical, platelike ing in the rupture of molluscum bodies. Sites of varying fric- structures with notched corners were revealed (Figure 2A). His- tion might explain why some molluscum papules developed topathologic analysis of the excised nodule demonstrated the around an EAC-like reaction, but others, owing to less fric- presence of a superficial epidermal cyst with squamous epithe- tion on the right lower abdomen and bilateral posterior lial lining containing several cholesterol clefts (Figure 2B). A large thighs, did not. area of the lesion was filled by a foreign-body, giant-cell reac- In conclusion, our case illustrates EAC as a reaction pat- tion and some red blood cell extravasations. tern that could be induced by molluscum contagiosum. It probably represents an immunologic reaction to viral anti- Discussion | An epidermal cyst is a common, keratin-filled, epi- gens. Clinicians should keep this phenomenon in mind thelial-lined cyst of the skin. It is usually a slow-growing, while dealing with patients with EAC or molluscum conta- asymptomatic, dermal or subcutaneous elastic nodule that may giosum. be skin colored or yellowish white when located near the skin surface. The cyst may be connected to the surface by a duct, Chien-Ho Chu, MD and the clinical identification of the corresponding pore rep- Pei-Keng Tuan, MD resents a diagnostic clue. Two previous studies have high- Shih-Jyun Yang, MD lighted the usefulness of dermoscopy in identifying the pore, described as a keratin-filled, roughly circular orifice that may Author Affiliations: Department of Dermatology, Cathay General Hospital, be whitish, yellow, brown, or black.1,2 Taipei, Taiwan. In our case, dermoscopy of the nodule revealed the pres- Corresponding Author: Pei-Keng Tuan, MD, Department of Dermatology, ence of the pore along with 2 sharply demarcated areas, each Cathay General Hospital, 280 Renai Rd, Sec 4, Taipei, Taiwan showing a different color. Histopathologic analysis showed an ([email protected]). epidermal cyst corresponding to the yellowish area along with Published Online: August 5, 2015. doi:10.1001/jamadermatol.2015.2075. a foreign-body giant-cell reaction and red blood cell extrava- Conflict of Interest Disclosures: None reported. sations, likely the result of the cyst rupture, responsible for the Additional Contributions: We are indebted to Cher-Wei Liang, MD, National 3 Taiwan University Hospital, Taipei, and Cheng-Hsiang Hsiao, MD, Cheng Hsin bluish color. General Hospital, Taipei, who reviewed the tissue samples for histologic A noninvasive technique, RCM is increasingly being used evaluation. They received no compensation for their contributions beyond that for several dermatologic conditions other than melanocytic received in the normal course of their employment. tumors.4,5 Unlike conventional vertical histopathologic sec- 1. Kipping HF. Molluscum dermatitis. Arch Dermatol. 1971;103(1):106-107. tions, it provides 2-dimensional pictures representing hori- 2. Rocamora V, Romaní J, Puig L, de Moragas JM. Id reaction to molluscum zontal (en face) scans of the skin. Superficial laser depth pen- contagiosum. Pediatr Dermatol. 1996;13(4):349-350. etration (250 μm) represents a limitation in the assessment of 3. Lee YB, Choi HJ, Park HJ, Lee JY, Cho BK. Two cases of erythema multiforme associated with molluscum contagiosum. Int J Dermatol. 2009;48(6):659-660. epidermal cysts, which are generally located deeper in the der- mis and the subcutis. In our case, RCM allowed us to identify 4. Attard NR, De Silva BD. Erythema multiforme associated with resolving molluscum contagiosum. Clin Exp Dermatol. 2007;32(2):214-215. not only the pore but also the duct underneath, which ap- 5. Vasily DB, Bhatia SG. Erythema annulare centrifugum and molluscum peared as a keratin-filled roundish canal penetrating down into contagiosum. Arch Dermatol. 1978;114(12):1853. the epidermis.

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