Mollusca contagiosa. Mollusca contagiosa are a common viral skin disease, which mainly affects young children. These umbilicated lesions, which are a few mm in size, are self-limiting; however, in some cases the course may be prolonged even for up to years. There are multiple methods of therapy. The author's favourite is liquid nitrogen cryosurgery for each individual lesion with the smallest spraytip for a couple of seconds.