Molluscum contagiosum infection on a congenital intermediate melanocytic naevus

A 2-year-old girl presented with a 3-month history of several small painless papules, growing on the surface of an abdominal congenital melanocytic naevus (MN). Her mother noted that the lesions were significantly increasing in number and size. There was no history of trauma and her medical and family histories were unremarkable. Physical examination revealed multiple skin-coloured, translucent, glossy, dome-shaped papules, ranging from 1 to 3 mm, localised exclusively on the surface of a macular, smooth, light to dark brown, non-hypertrichotic congenital intermediate MN (2×4 cm) (see figure 1). The dermoscopic examination of the papules suggested the diagnosis of molluscum contagiosum (MC), which was histologically confirmed. MC is a common viral skin infection, which is seldom associated with other skin diseases (eg, epidermoid cyst and nevocellular naevus).1 The localisation of MC on an MN is extremely rare, and only a few case reports have been published in the literature until now; in all reported cases, the lesions are strictly confined to the MN and did not affect the remaining skin.2 ,3 A possible explanation of the occurrence of viral lesions on an MN may be represented by the Meyerson’s phenomenon, an eczematous reaction occurring in MN.4 We could hypothesise that this resulted in a barrier dysfunction predisposing the patient to develop MC locally. Even though congenital intermediate MN is recognised to have a low malignancy potential during childhood,5 melanoma can develop. Therefore, the physician should be aware of the appearance of MC superinfection on MN, but the occurrence of new lesions within a congenital MN requires a dermatological evaluation