GP and hospital practitioner Dr Andy Jordan presents the latest in his series on differentiating similar-looking skin conditions
Molluscum is relatively easy to diagnose in children, who often have multiple umbilicated pearly papules. But giant molluscum is trickier as the umbilication is often missing and the lesion is much larger than the smaller mollusca seen in children. Dermatofibromas and giant molluscum are both usually seen as single papules or nodules affecting young adults. But the lesions are worth differentiating because the aetiology and management are quite different.
Dermatofibroma
• Lesions are 1-5cm in diameter
• Usually a solitary, firm or hard nodule, but there may be two or three
• Most commonly found on lower legs of young adults
• Colour varies from pink to yellow/brown and a peripheral ring of deeper pigmentation may be seen
• May be slightly scaly
• Pruritus and tenderness may occur
• Dimpling may occur over the lesion when pinched due to the overlying epithelium being tethered to the underlying lesion
• More common in women than men
• Dermoscopy shows a white centre with a fine brown peripheral network
• Has traditionally been ascribed to reaction to an insect bite, but there is no clonal proliferation of dermal histocytes so a neoplastic process is now considered more likely
• There is no potential for malignancy
• No treatment needed unless diagnostic uncertainty exists or it is significantly tender.
Giant molluscum
• Lesions are 5-15mm in diameter
• Usually a solitary soft papule or nodule often on the face, but can occur on trunk or limbs
• Tends to occur in young adults
• Shiny pearly white/pink lesion with some whitish areas
• Asymptomatic
• More common in men than women
• Due to infection with Molluscum contagiosum virus – a Pox virus
• Widespread lesions should raise the question of immunosuppression, such as HIV, sarcoidosis or therapy-associated
• No treatment needed unless diagnosis is uncertain
• If diagnosis is uncertain, removal by curettage and cautery is appropriate.
Dr Andy Jordan is a GP and hospital practitioner in dermatology in Chesham, Buckinghamshire
