Molluscum Contagiosum Mimicking Verruca Vulgaris on the Sole

Dear Editor:

Molluscum contagiosum (MC) is a skin infection caused by Molluscum contagiosum virus of Poxviridae. It commonly affects the face, neck, and trunk, but, rarely, the sole is affected¹.

A healthy 30-year-old woman with four match head to pea size hyperkeratotic lesions on the left sole visited our clinic (Fig. 1A). These lesions had been present for several months. The lesions were painful while walking, and there was no prior history of trauma. The verrucous morphology of the largest skin lesion was similar to verruca plantaris, however, it was also accompanied by painful smooth white papules (Fig. 1B), which are unusual in verruca plantaris. Therefore, punch biopsy was performed to distinguish it from other skin diseases. Histopathological examination revealed the classic cup-shaped invagination of the epidermis into dermis and hyperplastic keratinocytes containing eosinophilic, intracytoplasmic inclusion bodies, confirming the diagnosis of MC (Fig. 2). In addition, human papilloma virus (HPV) polymerase chain reaction (PCR) test was performed to rule out co-infection with HPV, and the result was negative. She had no other underlying disorders. The residual papules were extracted with forceps to remove the lesions completely (Fig. 1C), and no recurrence was observed during the 3-month follow-up period.

Fig. 1. Clinical manifestation of plantar molluscum contagiosum. (A) Plantar molluscum contagiosum on the left sole presented as four hyperkeratotic papules and nodules (black arrows). The largest lesion shows prominent hyperkeratosis that mimics verruca plantaris. Punch biopsy was performed at the center of the largest lesion (black circle). (B) A close-up photo of the lowermost lesion showing a smooth white papule. (C) Protruded inclusion body during the extraction procedure (black arrow). We received the patient’s consent form about publishing all photographic materials.

Fig. 2. Histopathological examination showed numerous intracytoplasmic inclusion bodies confirming the diagnosis of molluscum contagiosum (A) in a low magnification (H&E, ×40) and (B) in a high magnification (H&E, ×100).

MC usually presents as skin-colored and rounded umbilicated papules. It is a common viral skin infection that mostly affects the face, neck, and trunk in school-aged children¹. In adults, MC mainly affects the genital region with an otherwise normal immune system, which is considered as a sexually transmitted infection¹. However, atypical presentations and atypical localizations such as soles and palms may occur², especially in immunocompromised individuals, and they may imitate other skin diseases such as verruca plantaris, eccrine poroma, foreign body granuloma, epidermoid cyst, and amelanotic melanoma. MC usually presents as asymptomatic, but more than half of the cases of plantar MC have been reported to be painful as the patient in this study³.

The main ways of transmission are direct contact with the infected skin and autoinoculation. Minor trauma or plantar hyperhidrosis has been reported as a predisposing factor for the transmission of the disease³. Since MC is a highly prevalent infection, it is not known why it does not appear more often on the soles unlike the papilloma virus. García-Montero et al.⁴ speculated that this may be because the poxvirus (150~300 nm) is much larger than the human papillomavirus (60 nm), and this makes it difficult to invade the thick layer of the stratum corneum on the sole.

Several treatments are available for MC lesions, including potassium hydroxide, salicylic acid, hydrogen peroxide, cryotherapy, curettage, and pulsed dye laser⁵. Treatment should be based on the location, size, number of lesions, and patient’s health because of the self-limited nature of MC⁵. The patient in this case did not have any underlying disease and had only four MC lesions, so it was successfully treated with physical removal.

Herein, we report an unusual presentation of MC on the sole, which needs to be differentiated from other diseases of the plantar nodule.