In 1817, long before the recent increased incidence of molluscum contagiosum (MC), Bateman first described milky fluids that could be expressed from characteristic lesions. Henderson and Paterson, 2 researchers studying molluscum contagiosum independently 25 years later, described the milky fluid to be cellular. Only later did the 2 researchers realize they had discovered the hallmark intracytoplasmic inclusion body, appropriately named the Henderson-Paterson body (molluscum body).
Until the early 20th century, the medical community remained unsure of the etiology of molluscum contagiosum. Certain authorities believed the papules to be enlarged sebaceous glands, while others postulated that a parasitic infestation caused the lesions. A breakthrough in the study of molluscum contagiosum occurred in 1905 when Juliusburg discovered and documented the viral nature of molluscum contagiosum.
The molluscum contagiosum virus, which contains linear double-stranded DNA, causes molluscum contagiosum. Restriction endonucleases have elucidated 4 discrete viral subtypes: molluscum contagiosum virus subtypes I, II, III, and IV. All subtypes are classified as members of the Orthopoxvirus genus or as unspecified poxviruses. When human infection occurs, the epidermal keratinocytes are targeted. Viral replication occurs within the cytoplasm of the infected cell, generating the characteristic cytoplasmic inclusion bodies. Histologically, these inclusion bodies are most evident within the stratum granulosum and stratum corneum layers of the epidermis. Hyperproliferation of the epidermis also occurs because of a doubling in the rate of cellular division of the epidermal basal layer.
The molluscum contagiosum virus causes 3 distinct disease patterns in 3 different patient populations: children, immunocompetent adults, and immunocompromised patients (children or adults). Children acquire the molluscum contagiosum virus through either direct skin-to-skin contact or indirect skin contact via fomites such as gymnasium equipment and public baths. Lesions typically occur on the chest, arms, trunk, legs, and face. In adults, molluscum contagiosum is considered a sexually transmitted disease (STD). In almost all cases involving healthy adults, patients exhibit few lesions, which are limited to the perineum, genitalia, lower abdomen, or buttocks. Generally, in immunocompetent populations, molluscum contagiosum is a self-limited disease.
Patients infected with human immunodeficiency virus (HIV) or patients who are otherwise severely immunologically compromised may experience a longer course with more extensive and atypical lesions. In patients infected with HIV, lesions generally are distributed more widely, frequently occur on the face, and may number in the hundreds. The cutaneous manifestations of other opportunistic infections, such as cutaneous cryptococcosis, histoplasmosis, and aspergillosis, may mimic molluscum contagiosum and must be ruled out in immunocompromised hosts.
For additional information on HIV, see Medscape’s HIV Transmission & Prevention Resource Center.
The incidence of molluscum contagiosum rose from 1960-1980. It is less common than other STDs, occurring in about 1% of the general population. In a 1984 paper published in the Urologic Clinics of North America, Margolis of the Centers for Disease Control and Prevention reportedthat 1 case of molluscum contagiosum occurs for every 42-60 cases of gonorrhea infection.[22]
The prevalence rate in the population infected with HIV is reported to be 5-18%. In patients who are infected with HIV and who have CD4 cell counts of less than 100 cells/μL, the prevalence of molluscum contagiosum is reported to be as high as 33%.
Mortality/Morbidity
Molluscum contagiosum is a self-limited disease in immunocompetent individuals, with no long-term complications or sequelae.
In contrast, molluscum contagiosum infection in patients who are infected with HIV may result in conspicuous cosmetic deformities that may have significant adverse psychological effects.
Although superinfection and cellulitis have been reported to occur in the setting of molluscum contagiosum in the population infected with HIV, no mortality has been associated directly with the molluscum contagiosum virus.
Race
No racial predilection has been reported.
Sex
The incidence in men reportedly is greater than that in women.
Age
Molluscum contagiosum has been reported in all age groups but is observed most commonly in children and adults who are sexually active. Molluscum contagiosum may occur at any age in immunocompromised patients.
Parents may report recent exposure to other children affected with molluscum contagiosum at school, camp, or public recreational facilities (eg, gymnasiums, swimming pools).
Children frequently have active atopic dermatitis.
Immunocompetent adults
Affected adults who are otherwise healthy uniformly are sexually active but may not know that their partners are affected.
Having multiple sexual partners increases the risk of infection; the frequency of unprotected sex increases the risk of transmission.
Patients infected with HIV
Patients generally have low CD4 counts, and the severity of infection is inversely related to the patient's CD4 count.
Patients who are poorly compliant or noncompliant with highly active antiretroviral therapy (HAART) for the treatment of HIV are at an increased risk, as are those who have multiple sexual partners.
The frequency of unprotected sex also increases the risk of transmission.
Miscellaneous
A recent report detailed an eruption of molluscum contagiosum in a patient who had undergone a renal transplant.[21]
Case reports detail molluscum contagiosum eruptions in areas that are treated with tacrolimus 0.1% (Protopic).[2, 14, 42]
Individual lesions are typically discrete, waxy, flesh-colored, dome-shaped, umbilicated papules with a smooth surface. Lesions may be few or numerous, depending on the immunological status of the host. In all patients, lesions generally are asymptomatic, but pruritus and/or perilesional eczematous reactions may develop.
In children and healthy adults
Lesions are usually 1-2 mm in diameter and number fewer than 20.
In children, lesions generally are distributed on the trunk, arms, legs, and face.
In immunocompetent adults, lesions usually are found on the genitalia, lower abdomen, inner upper thighs, and/or buttocks.
The average duration of an untreated lesion is 6-9 months but may be as long as 5 years.
Individuals who are HIV positive
The disease is generally more severe in patients infected with HIV. Lesions may number in the hundreds and are generally larger (can be >2 cm in diameter) and more deforming and may be confluent.
In addition to groin involvement, lesions frequently are found on the face. The duration of untreated lesions may be 5 years or more because molluscum contagiosum may not be self-limiting in this population.
In both immunocompetent and immunocompromised individuals, molluscum contagiosum is rarely found in the oral mucosa and conjunctiva.
The prototypical hematoxylin and eosin (H&E)–stained histological section of molluscum contagiosum reveals a cup-shaped indentation of the epidermis into the dermis (as seen in the image below).
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This low-power view of a molluscum contagiosum (MC) lesion shows the classic cup-shaped invagination of the epidermis into dermis. The Henderson-Pater....
Within the region of the indentation, the epidermis appears thickened (acanthosis) compared to the surrounding uninvolved skin, and the cornified layer typically is disintegrated. The striking feature is the presence of intracytoplasmic, eosinophilic, granular inclusions within the keratinocytes of the basal, spinous, and granular layers of the epidermis (as seen in the image below).
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This is a medium-power view of a molluscum contagiosum (MC) lesion. Magnification allows better demonstration of the intracytoplasmic molluscum bodies....
These inclusions, termed molluscum bodies or Henderson-Paterson bodies, can measure 35 µm in diameter and tend to displace the nucleus to the periphery of the cell. Ultrastructural studies have shown that the molluscum bodies are membrane-bound sacs that contain numerous molluscum contagiosum virions. The surrounding dermis is relatively unremarkable.
In nonprototypical cases, in which intradermal rupture of molluscum bodies occurs, an intense dermal inflammatory infiltrate consisting of lymphocytes, histiocytes, and occasional foreign body–type multinucleated giant cells may be observed. Rarely, metaplastic ossification may occur. Exceptionally, the dermal inflammatory infiltrate may be intense enough to simulate a cutaneous lymphoma (pseudolymphoma).
The course of molluscum contagiosum usually is self-limited, and lesions generally heal without scarring.
Intervention may be indicated if lesions persist. Therapeutic modalities include topical application of various medications, radiation therapy, and/or surgery. Each technique might result in scarring or postinflammatory pigmentary changes. Frequently, multiple treatment sessions are necessary because of the recurrence of treated lesions and/or the appearance of new lesions by autoinoculation. The benefit of therapy must exceed the risk.
The Food and Drug Administration (FDA) has approved none of the topical or intralesional agents for treatment of molluscum contagiosum.
Topical therapy: Clinical success has been reported with the use of the following topical agents, which may act as irritants, stimulating an immunological response.
Imiquimod cream is an immune response modifier approved for the treatment of external genital and perianal warts in adults. It has been reported to be effective in the treatment of molluscum contagiosum.[7, 38] Imiquimod cream may be used in conjunction with cantharidin.[33]
Several studies report that cantharidin, a chemovesicant, is effective in treating molluscum contagiosum. To test the patient's response to therapy, treat only a few lesions on the initial visit. Cantharidin may be used in combination with imiquimod.[33]
Tretinoin has reportedly been successful in the treatment of small molluscum contagiosum lesions. Tretinoin, cantharidin, and imiquimod may be dispensed to the patient with application instructions and close follow-up.
Bichloracetic acid, trichloroacetic acid, salicylic acid, lactic acid, glycolic acid, and silver nitrate also have been used, but the physician must apply them in the office.
Topical podophyllotoxin 0.5% cream self-administered twice daily for 3 weeks has been reported effective in one placebo-controlled, double-blind study.[37]
Reports have suggested that subcutaneous interferon alfa (IFN-alfa) administered intralesionally may be useful in immunocompromised children.
A recent case report noted the efficacy of topical cidofovir in the treatment of disseminated molluscum in immunodepressed patients.[14] Cidofovir diphosphate was reported to inhibit molluscum contagiosum virus DNA polymerase activity.[39]
Frequently, multiple treatment sessions are necessary because of recurrence of treated lesions and/or the appearance of new lesions by autoinoculation. Each technique may result in scarring or postinflammatory pigment changes.
Curettage: Individual lesions may be removed with a hand-held curette, with little discomfort. Follow curettage with application of a topical irritant.
Cryosurgery: Apply liquid nitrogen for 10-15 seconds per lesion. Liquid nitrogen therapy may be painful and can result in blistering. Temporary or permanent depigmentation may occur in individuals who are more darkly pigmented.
Electrodesiccation may be used for lesions that are refractory to curettage or cryosurgery. This technique can cause significant discomfort; consider using local anesthesia. Use caution in patients with pacemakers.
Pulsed dye laser has been used with some success.[25]
Intense pulsed light (IPL) has also been used in conjunction with the application of 5-aminolevulinic acid with success in a 6-case patient series.
These are first-line topical agents, although they are not FDA approved for molluscum contagiosum. Effectiveness against warts may result from exfoliation.
Clinical Context:
Inhibits microcomedo formation and eliminates lesions. Makes keratinocytes in sebaceous follicles less adherent and easier to remove. Available as 0.025%, 0.05%, and 0.1% creams. Available also as 0.01% and 0.025% gels.
Begin with lowest tretinoin formulation and increase as tolerated.
Clinical Context:
Cauterizes skin, keratin, and other tissues. Although caustic, causes less local irritation and systemic toxicity than other medications in the same class. Response often is incomplete, and recurrence is frequent.
The agents are used to aid in the removal of keratin in hyperkeratotic skin disorders, including corns, ichthyoses, common warts, flat warts, and other benign verrucae.
Interferon alfa 2a and 2b (Roferon-A [alfa-2a], Intron A [alfa-2b])
Clinical Context:
Protein product manufactured by recombinant DNA technology. Mechanism of antitumor activity is not understood clearly; however, direct antiproliferative effects against malignant cells and modulation of host immune response may play important roles.
Autoinoculation may result from trauma, such as shaving, as well as manipulation of lesions by the patient.
Cellulitis is an unusual complication of molluscum contagiosum in patients who are HIV infected.[15] Secondary infection with Staphylococcus aureus has resulted in abscess formation, whereas Pseudomonas aeruginosa can cause necrotizing cellulitis.
Spontaneous resolution generally occurs by 18 months in immunocompetent individuals; however, lesions have been reported to persist for as long as 5 years.
The duration of infection is uncertain in populations with HIV infection and in populations that are otherwise immunocompromised (eg, patients who have undergone renal transplant) because molluscum contagiosum may not be self-limiting in these cases.
Ashish C Bhatia, MD, FAAD, Assistant Professor, Department of Dermatology, Northwestern University, Feinberg School of Medicine; Director of Clinical Research, Department of Dermatology and Dermatologic Surgery; Director of Dermatologic Surgery and Dermatology, The Dermatology Institute of DuPage Medical Group
Disclosure: Nothing to disclose.
Coauthor(s)
David Rowe, MD, Pathologist, Laboratory Medicine, Martha Jefferson Hospital
Disclosure: Nothing to disclose.
Julia R Nunley, MD, Professor, Program Director, Dermatology Residency, Department of Dermatology, Virginia Commonwealth University Medical Center
Robert Orenstein, DO, Associate Professor, Department of Medicine, Medical College of Virginia, Virginia Commonwealth University; Medical Director, Infectious Disease Clinic, Medical College of Virginia Hospitals
Disclosure: Nothing to disclose.
Seth Forman, MD, Private Practice, Tampa, Florida
Disclosure: Abbott Laboratories Honoraria Speaking and teaching
Tracy Campbell, MD, Staff Physician, Department of Dermatology, Rush Medical Center
Disclosure: Nothing to disclose.
Specialty Editors
Daniel R Lucey, MD, MPH, Chief, Fellowship Program Director, Department of Internal Medicine, Division of Infectious Diseases, Washington Hospital Center; Professor, Department of Internal Medicine, Uniformed Services University of the Health Sciences
Disclosure: Nothing to disclose.
Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment
John W King, MD, Professor of Medicine, Chief, Section of Infectious Diseases, Director, Viral Therapeutics Clinics for Hepatitis, Louisiana State University Health Sciences Center; Consultant in Infectious Diseases, Overton Brooks Veterans Affairs Medical Center
Disclosure: emedicine $50.00 author of chapter; MERCK None Other
Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital
Disclosure: Nothing to disclose.
Chief Editor
Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital
This low-power view of a molluscum contagiosum (MC) lesion shows the classic cup-shaped invagination of the epidermis into dermis. The Henderson-Paterson bodies are identified readily and stain purple-to-red in this image.
This is a medium-power view of a molluscum contagiosum (MC) lesion. Magnification allows better demonstration of the intracytoplasmic molluscum bodies (staining purple-pink) within the keratinocytes.
Presented here are the classic umbilicated papules of molluscum contagiosum (MC) lesions on the cheek of a child. Facial lesions occur frequently in children, although lesions generally are few.
Molluscum contagiosum (MC) rarely occurs on the face in an adult unless the patient is infected with HIV. When MC occurs in individuals infected with HIV, facial lesions are common and frequently numerous.
Molluscum contagiosum (MC) lesions in individuals infected with HIV may number in the hundreds. In addition, they may become quite large and prominent.
This low-power view of a molluscum contagiosum (MC) lesion shows the classic cup-shaped invagination of the epidermis into dermis. The Henderson-Paterson bodies are identified readily and stain purple-to-red in this image.
This is a medium-power view of a molluscum contagiosum (MC) lesion. Magnification allows better demonstration of the intracytoplasmic molluscum bodies (staining purple-pink) within the keratinocytes.
This molluscum contagiosum body is an intracytoplasmic inclusion body. Notice in the image that the keratinocyte nuclei are displaced to the periphery of the cell and the intracytoplasmic inclusions have a granular quality.
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