Contagious mollusc B08.1

Bateman, 1817; Henderson, 1841; Juliusberg, 1905.

Bateman first used the term Molluscum contagiosum in 1817.

Henderson first described "globoid corpuscles" in the lesions in 1841

Juliusberg succeeded in 1905 in transmitting the infection from person to person.

A chronic, localized, only rarely generalized (immunodeficiency), self-limited infectious disease of the skin that is widespread throughout the world and is harmless under normal immune conditions. It is caused by the Molluscum contagiosum virus from the Poxviridae group (see poxviruses below). Infection with the virus is not cyclic. Viremia does not occur.

Molluscum contagiosum viruses (MCV; molluscipoxvirus) of subtypes I-IV. These are cuboidal DNA viruses from the Poxviridae group (size: 360 x 219 nm). MCV I is found in about 95% of cases, MCV II in 3-5% of cases. MCV III or IV is very rarely detected intralesionally.

Molluscum contagiosum is one of the 50 most common diseases worldwide.

There is no sex predisposition.

Molluscum contagiosum is common worldwide with increasing incidence (0.1-1.2% of the population depending on the region) and endemics.

Frequent in tropical areas.

Especially in young children and adolescents. In a larger study (n=277), children and adolescents between 1-14 years (average 6.7 years) were affected.

Incubation period: is 2-7 weeks.

Patients with atopic eczema tend to have an increased incidence (disseminated incidence is possible here = Eccema molluscatum). Approximately 25% of those affected also suffer from atopic eczema(of varying intensity).

Infection often occurs after swimming pool visits, e.g. after bathing infants in warm paddling pools.

Also in immunosuppressed adult patients (e.g. AIDS patients; lymphoma patients).

Especially on the upper body, upper arm, axillary fold. The combination of arms and trunk is the most common. More rarely: face, eyelids, neck, perianal and perigenital region.

Predominantly occurring in multiple cases (about 75% of those affected have > 20 Dell's warts).

Mostly scattered or grouped, regionally limited, more rarely also generalized, occasionally arranged in lines (Koebner phenomenon), firm, 0.1-0.4 cm large, usually broadly seated, less frequently pedunculated (see Molluscum contagiosum pediculatum), centrally dented, waxy, whitish, yellowish or pale pink nodules. A whitish, greasy mass can be expressed after scoring the surface.

In rare cases molluscs reach a size of up to 1.5 cm (see below Molluscum contagiosum giganteum).

In immunocompromised patients (see below organ transplants, skin changes) and children with atopic eczema (see Eccema molluscatum), mollusca contagiosa can eruptively generalize > 100 molluscs (comparable to Eccema herpeticatum) or merge into large (up to 10 cm in diameter) plaques.

Verrucae planae-like type: Rarely a small papular "Verrucae planae-like type" is seen in small children with a miliary or also herd-shaped grouped, completely asympomatic sowing of smallest, skin-coloured papules on the trunk and face. This form has a high tendency to spontaneous regression.

Epithelial acanthoma consisting of several lobules that extend deep into the dermis. The centre is cratered. Here cellular detritus and so-called molluscum corpuscles ("Henderson-Paterson Bodies"): nuclear, homogeneous, dark red-violet stained, epithelial cell-like, ovoid formations = virus-infested epidermis cells. In early lesions with moderate acanthosis, small eosinophilic, intracytoplasmic inclusion bodies are found in the distended suprabasal keratinocytes. In the dermis accompanying lympho-histiocytic infiltrate.

Clinical:

• Xanthoma: yellowish, firm, no umbilication of the surface; usually older age.
• Xanthelasma: typical localization is the eyelid area. No central umbilication
• Milia: small, firm white horny beads, not exophytic
• Verrucae vulgares: verrucous, not shiny surface
• Syringoma: usually in the lid area, only flatly protuberant. Higher age

Histological:

• Verruca vulgaris: viral acanthoma also with inclusion bodies. However, these do not show the typical features of molluscum corpuscles (dark red purple colored homogeneous inclusion corpuscles with peripheral nucleus).

Bacterial superinfection due to contamination with pyogenic germs.

Itching with scratching effects and (auto)inoculation of further molluscum contagiosum viruses, see also Eccema molluscatum.

The treatment of choice for isolated mollusca contagiosa is curettage in LA.

• Curettage: Tighten the surrounding skin with two fingers, apply a small non-cutting curette by levering it at the base of the molluscum and spoon it out against the skin resistance. If necessary, raised wound edges can still be smoothed with a cutting curette (e.g. boot no. 3 or 4). Preoperatively: It is recommended to mark each molluscum the day before surgery (preferably performed by the parents).
• Chemical destruction: Apply 10% KOH solution daily to the molluscs with a zinc paste while covering the area until an inflammatory reaction occurs. A study comparison with Imiquimod showed an equivalent result of both therapeutic modalities (healing rate of 40% after 12 weeks of therapy).
• Alternative:
  • Scarification with a cannula and expression of the individual foci (too cumbersome with a large number of molluscs).
  • In case of localized infestation, a trial with a vitamin A acid cream (e.g. Isotrex) can be made; application 2 times daily.
  • Reported success with laser therapy(erbium YAG laser, CO ₂ laser, dye laser).
• Experimental:
  • Good results (up to 69% response rate) have been reported using topical treatment with 5% imiquimod cream(3 times/week for several weeks or, according to another study, treatment 1 time/day in the evening and wash off in the morning) have been described in smaller studies. Cave: No approved indication.
  • Cidofovir promoted as "last chance" (approval for CMV retinitis). Cidofovir can be applied as 1% cream (Cave: extremely high price!).

Complications:

• Individual molluscs show inflammatory focal reactions (e.g. due to mechanical irritation). In these cases local anesthesia is not sufficient.
• It is not uncommon for molluscs to occur in children with atopic eczema. In this constellation, superimposed pyoderma is often observed. It is recommended to first treat the pyoderma and eczema consistently for a few days, e.g. with 1% hydrocortisone and 2% clioquinol-containing cream R052.
• Postoperative: Wound centers are dressed with a dressing containing polyvidone iodine (e.g. Betaisodona). This is renewed by the patient the following day. Wound sites generally heal without complications and also without scarring. In case of extensive infestation or recurrence, follow-up treatment with Imiquimod (Aldara).

Anaesthesia: In the case of some molluscs, even small children can be treated without general anaesthesia. It is recommended to treat the affected areas preoperatively for 1/2 hour with a 5.0% Lidocaine Prilocaine cream (e.g. EMLA® cream) occlusively. Due to the formation of methhemoglobin in children, the recommended maximum amounts should be observed: 1g in children < 5kgkgkg; <2g in children <10kgkg; <20g in children over 20kgkg. If necessary, a combination of local anaesthesia with systemic midazolam administration (e.g. Dormicum) may be appropriate. In case of extensive infestation, general anesthesia is preferable.

In follow-up examinations of larger collectives, mollusca contagiosa heals with and without therapy within 1-62 months (average after 13 months).

In about 50% of children, healing can be expected within 12 months.

Mollusca contagiosa can still be detected in about 30% of the children after 18 months, in about 15% after 24 months.

A longer duration of the disease or a larger number of mollusca contagiosa are associated with a reduced quality of life of the affected persons.

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