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Erythema annulare centrifugum (EAC), whether as a distinctive entity or a reaction pattern, manifests characteristic clinical and histopathologic features. It has been associated with infectious agents, particularly dermatophytes, other fungi (eg, Candida species, Penicillium species), bacteria (eg, Mycobacteria species, Streptococcus species, Escherichia coli), viruses (eg, poxvirus, Epstein-Barr virus, varicella-zoster virus, human immunodeficiency virus), and parasites. Less commonly, EAC has been linked to drugs, connective-tissue disease, sarcoidosis, hypereosinophilic syndrome, and pregnancy. However, many of these associations are likely coincidental, and in most cases, no underlying cause is identified. Herein, we report a case of EAC caused by molluscum contagiosum.
A 45-year-old man, in relatively good health, presented with several gradually enlarging plaques on the bilateral upper thighs of 1 month’s duration. On physical examimation, several annular plaques, 0.5 to 5.0 cm in diameter, with raised edges and trailing scales behind advancing borders were found on the bilateral upper thighs and left inguinal area (Figure 1A). In the center of each plaque, there was a single 2-mm reddish-brown shiny papule (Figure 1B). In addition, some smooth, shiny, pearly, and firm papules without peripheral erythema were also observed on the right lower abdomen and the bilateral posterior thighs. He reported that these lesions were sometimes itching and sometimes painful.
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.
A skin biopsy specimen was obtained from the central papule on the right upper thigh. Histopathologic examination showed lobulated, endophytic epidermal hyperplasia, with a very large eosinophilic intracytoplasmic inclusion in each keratinocyte (Figure 2A). These features demonstrated molluscum contagiosum. Heavy superficial perivascular lymphohistiocytic infiltrates, focal basal vacuolization, mild spongiosis, and mounts of parakeratosis were also observed around the main lesion (Figure 2B). These peripheral findings were compatible with the histopathologic features of superficial EAC.
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).
Molluscum contagiosum is a common epidermal infection caused by a poxvirus of the Molluscipox virus genus. Approximately 10% of patients develop an eczematous reaction around the central molluscum papules.1 Other unusual reactive processes associated with molluscum infestation include id reaction,2 erythema multiforme,3,4 and erythema annulare centrifugum.5,6 Erythema annulare centrifugum associated with molluscum contagiosum was first described by Vasily and Bhatia5 in 1978. To our knowledge, there are only 2 reports of this phenomenon in the literature. Based on the characteristic finding of annular erythema with trailing scale behind the advancing erythematous edge and compatibility of the histopathologic findings in our case, we diagnosed molluscum contagiosum–induced EAC. All lesions resolved within 2 weeks after cryotherapy for molluscum papules and topical treatment with fluocinonide, 0.05%, cream for peripheral erythema.
The pathogenesis of molluscum contagiosum–associated reactions remains obscure. One hypothesis has proposed that rupture and discharge of molluscum bodies into the surrounding dermis elicits an immunologic reaction that clinically presents as dermatitis surrounding inflamed molluscum papules.3 In our case, EAC-like reaction was mainly confined to the lesions on intertriginous areas and the right lateral thigh, which were prone to friction, resulting in the rupture of molluscum bodies. Sites of varying friction might explain why some molluscum papules developed around an EAC-like reaction, but others, owing to less friction on the right lower abdomen and bilateral posterior thighs, did not.
In conclusion, our case illustrates EAC as a reaction pattern that could be induced by molluscum contagiosum. It probably represents an immunologic reaction to viral antigens. Clinicians should keep this phenomenon in mind while dealing with patients with EAC or molluscum contagiosum.
Corresponding Author: Pei-Keng Tuan, MD, Department of Dermatology, Cathay General Hospital, 280 Renai Rd, Sec 4, Taipei, Taiwan (firstname.lastname@example.org).
Published Online: August 5, 2015. doi:10.1001/jamadermatol.2015.2075.
Conflict of Interest Disclosures: None reported.
Additional Contributions: We are indebted to Cher-Wei Liang, MD, National Taiwan University Hospital, Taipei, and Cheng-Hsiang Hsiao, MD, Cheng Hsin General Hospital, Taipei, who reviewed the tissue samples for histologic evaluation. They received no compensation for their contributions beyond that received in the normal course of their employment.
Chu C, Tuan P, Yang S. Molluscum Contagiosum–Induced Erythema Annulare Centrifugum. JAMA Dermatol. 2015;151(12):1385–1386. doi:10.1001/jamadermatol.2015.2075
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