Subungual Molluscum Contagiosum: A Rare Presentation

• Molluscum contagiosum can affect any site of the body, but the lower abdomen, thighs, genitals, and perianal area are the sites most commonly involved.

• Oral, ocular, and plantar regions are unusual localizations reported for molluscum contagiosum.

• MC occur rarely in the subungual area.

• Subungual MC may imitate subungual warts, digital fibrokeratomas, and melanomas.

• Dermoscopy may help to diagnose subungual MC.

Molluscum contagiosum (MC) is a self-limited, viral, infectious, cutaneous disease caused by the MC virus that belongs to the Poxviridae family. Sexual or nonsexual direct contact with the infected skin and autoinoculation are the main transmission ways. MC is usually characterized by pinkish to skin color and round umbilicated papules varying in size and shape. The diagnosis is usually based on clinical findings [1]. Here, we report a case of MC with atypical localization, which was initially mis-diagnosed as viral wart.

A 24-year-old male having a painless subungual mass of 3 weeks duration on the great toe of his left foot was referred to us with a diagnosis of subungual wart. Physical examination revealed confluent pinkish papules on the hyponychium (Fig. 1a). The patient had no similar lesion elsewhere. Dermoscopic examination revealed polylobular, roundish, white to yellow structures along with punctiform/dotted and serpentine vessels (Fig. 2). Serological investigations including HIV and the venereal disease research laboratory test were within normal limits. The patient was treated with a total shave excision of the lesion followed by immediate cryotherapy. A preliminary diagnosis of MC, viral wart, and fibrokeratoma was made. Histopathological examination of the excision specimen showed numerous Henderson-Paterson bodies (intracytoplasmic hyaline eosinophilic inclusion bodies) confirming the diagnosis of MC (Fig. 3). The surgical procedure applied allowed complete removal of the lesion, and no recurrence was observed after 3 months (Fig. 1b).

MC is a common infectious skin disease which affects both genders and may occur in all age groups. It may present with single, multiple, or grouped lesions. MC is usually self-limiting in a period of 6–9 months in the majority of cases; however, in rare cases, it may persist for years. MC can affect any region; however, the lower abdomen, thighs, genitals, and perianal area are the sites most commonly involved [1]. Subungual MC is extremely rare, and only 1 case has been published in the literature. Başaran et al. [2] reported a case of MC localized on the hyponychium of the middle finger of the right hand in a young woman. Oral, ocular, and plantar regions are other unusual MC localizations reported [3-5].

MC may present atypically with giant, eczematous, and follicular lesions [6-8]. The atypical manifestations may strongly imitate many cutaneous conditions, including warts, basal cell carcinoma, intradermal nevus, keratoacanthoma, and amelanotic melanoma [6]. The diagnosis of MC may be a real challenge especially in HIV-infected individuals [9]. Other causes of immunosuppression may also lead to atypical presentations. Our patient had no history of systemic disease and immunosuppression. HIV serology was also negative.

Dermoscopy has recently been an indispensable part of dermatology practices. Dermoscopic features of molluscum are well described. Polylobular, roundish, white to yellow structures and peripheral crown vessels are characteristic dermoscopic findings [1]. Radial and punctiform vessels may also be seen [10]. In our case, we observed polylobular, roundish, white to yellow structures along with punctiform/dotted and serpentine vessels. The main differential diagnosis in our case was subungual wart, in which dermoscopy usually shows a lobulated surface with thrombosed capillaries giving a so-called frog spawn appearance [11]. Although dermoscopy is an important auxiliary diagnostic tool, the final diagnostic confirmation is always based on histopathological examination.

To the best of our knowledge, subungual MC localized on the toe has not been described before.

A written informed consent was obtained from the patient for the publication of this case report and accompanying images. The authors have no ethical conflicts to disclose.

The authors have no conflicts of interest to declare.

There were no funding sources.

Ömer Faruk Elmas: concepts, design, definition of intellectual content, literature search, data acquisition, and manuscript preparation.

Asuman Kilitçi: manuscript editing, manuscript review, literature search, and data acquisition.