Molluscum Contagiosum
Key Points
Molluscum contagiosum (MC) is a benign viral infection found more commonly in warm, moist climates
It is transmitted from one host to another by direct contact with infected skin or through fomites on clothing or towels
MC is caused by a large double-stranded DNA virus, a member of Poxvirus
Eyelid lesions typically present as asymptomatic, single or multiple, firm, dome-shaped, pink, or flesh-colored papules with a central area of umbilication that range in size from 2 to 6 mm, although lesions as large as 1.5 cm have been described
MC lesions are usually self-limited and will resolve over 6 to 9 months if left untreated in immunocompetent hosts
Treatment with topical preparations have been advocated, including retinoids, salicylic acid-lactic acid, and imiquimod
No single intervention is completely effective, but most patients can achieve resolution of a high proportion of lesions
Molluscum contagiosum (MC) is a benign viral infection characterized by flesh-colored, dome-shaped papules on the skin or mucous membranes. It was first described in 1811 by Thomas Bateman.1 In 1841, Henderson2 and Paterson3 in separate papers described intracytoplasmic inclusion bodies, referred to as molluscum bodies or now often referred to as Henderson-Paterson bodies, that distinguish these lesions histologically.
MC infection is very common, often cited to occur in between 2% and 8% of the population.4 However, more recent studies based on serology testing suggest a much higher infection rate in Australian and European healthy populations ranging from 14.8% to 30.3%.5
The virus is found more commonly in warm, moist climates worldwide6 and is transmitted between individuals by close physical contact.7 It most often affects children, immunosuppressed individuals, and sexually active adults.6,8 In immunosuppressed individuals, the disease is typically more extensive.6 Rarely, vertical transmission can result in congenital MC.9,10
MC is transmitted from one host to another by direct contact with infected skin or through fomites on clothing or towels,11 and it can even be transmitted from contact sports.12 The average incubation time is between 2 and 7 weeks but can be as long as 6 months.13 Individual lesions are mostly 2 to 5 mm in diameter with a central umbilication, and papules usually occur in clusters. Swimming has been associated with a higher risk of developing MC.14 Among children, the risk of MC among swimmers is nearly twice that of nonswimmers,15 and the risk for children who swim frequently is about twice as high as the risk for those who use swimming pools infrequently.16
Several studies in Europe and the United States have reported an association between atopic dermatitis and MC ranging from 18.2% to 43%.17,18,19 However, a prospective observational pediatric study in Brazil found no relationship between MC and the development of atopic dermatitis.20
Etiology and Pathogenesis
MC is a contagious viral skin infection caused by the MC virus. This is a large double-stranded DNA virus, a member of the Poxvirus family.28 There are four subtypes of the molluscum contagiosum virus (MCV-1, MCV-2, MCV-3, and MCV-4), based on genetic polymorphisms, but their clinical manifestations are all similar.29 MCV-1 is the most common genotype seen in 75% to 96% of cases.11,30,31 The MCV is distinct from other poxviruses and is specialized to infect human skin, both because of its growth habit and its ability to evade local immune defenses.31 The virus propagates in differentiating cells of the human epidermis but does not cross the basement membrane, thus avoiding immune surveillance that would otherwise cause a systemic immune response. Free virus cores have been found in all layers of the epidermis, and the molluscum bodies contain large numbers of maturing virions. These are intracellular collagen-lipid-rich saclike structures that are thought to deter immunological recognition by the host.32
Clinical Characteristics
In children, the most commonly affected sites are the trunk, extremities, genitals, and face.33,34 Involvement of the oral mucosa is also seen but is rare.35 In adults, lesions are more often located on the lower abdomen, thighs, genitals, and perianal area,36 reflecting the common mode of acquisition
through sexual contact.37 Less common sites include the areola, eyelids, and fingers. MC rarely involves the mucosa of the lips,38 buccal mucosa,39 and conjunctiva.40 In immunosuppressed patients, lesions may be more extensive, larger, and more refractory to treatment.41,42,43
through sexual contact.37 Less common sites include the areola, eyelids, and fingers. MC rarely involves the mucosa of the lips,38 buccal mucosa,39 and conjunctiva.40 In immunosuppressed patients, lesions may be more extensive, larger, and more refractory to treatment.41,42,43
Eyelid MC typically presents as asymptomatic, firm, dome-shaped, pink, or flesh-colored papules (Figure 88.1). They may be single or multiple (Figure 88.2), occur on the upper or lower eyelid or both, and range in size from 2 to 6 mm, although lesions as large as 1.5 cm in diameter have been described (Figure 88.3).44 When multiple, the number of individual lesions on any individual is generally fewer than 20 in immunocompetent hosts, but occasionally can be more than 100.45 MC papules contain a white, waxy curd-like core and a central area of umbilication is a distinguishing feature. But, in some lesions, the umbilication may not be visible. Occasionally, lesions can be pruritic, tender to touch, or even painful. A case of MC papule has been associated with a cutaneous horn.46 Several cases of eyelid MC with secondary infection, abscess, and cellulitis have been reported.47,48,49 Rarely, MCV lesions occur on the conjunctiva.23,50,51 MC infects patients at all ages from early childhood to old age, but 65% of cases are aged 40 years or younger, with a mean age of about 30 years.52 Females represent slightly more than half of the reported cases. In immunocompromised hosts, lesions may be very numerous, very large, and confluent.
 FIGURE 88.1 A-D, Solitary, dome-shaped, umbilicated molluscum lesions of the eyelid. (B, Courtesy of Dr. Mohammad Javed Ali; D, Courtesy of Dr. Alan McNab.) |
Recently, Rosner and Zloto53 proposed a classification of periocular MC based on six different presentations. These are (1) umbilicated nodular; (2) big/giant; (3) conglomerated; (4) erythematous; (5) inflamed; and (6) pedunculated. The umbilicated nodular type is the most common,21 seen in nearly 66% of cases.53 This type may be singular or multiple, present at any age, and appear as white, pink, or flesh-colored, dome-shaped nodules with a central umbilication. The upper eyelid is more commonly involved, and lesions are usually unilateral, but occasionally can be bilateral. The inflamed type of MC lesion is reddish, tender, erythematous, and umbilicated with an inflammatory reaction.47 Big MC are lesions between 5 and 10 mm in diameter, and giant MC are larger than 10 mm.44 They are more common in children 1 to
5 years of age and in immunocompromised adults. Lesions are white, pink, or flesh-colored, dome-shaped nodules with no central umbilication.53,54 The erythematous presentation of MC appears with extensive erythema and surrounding scaling.53,55 The conglomerated type is not umbilicated so that the diagnosis is more difficult. Lesions are well-demarcated, white, sessile, and papillomatous aggregates of multiple microscopic MC nodules. The pedunculated type of MC is rare and protrudes like squamous papilloma.25,52
5 years of age and in immunocompromised adults. Lesions are white, pink, or flesh-colored, dome-shaped nodules with no central umbilication.53,54 The erythematous presentation of MC appears with extensive erythema and surrounding scaling.53,55 The conglomerated type is not umbilicated so that the diagnosis is more difficult. Lesions are well-demarcated, white, sessile, and papillomatous aggregates of multiple microscopic MC nodules. The pedunculated type of MC is rare and protrudes like squamous papilloma.25,52
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