Molluscum Contagiosum

Molluscum contagiosum is a viral infection limited to the epidermis and is common in children below 5 years of age. Lesions appear as grouped, flesh-colored, dome-shaped papules with central umbilication. Molluscum contagiosum is mild in immunocompetent patients and self resolves within months. Immunocompromised individuals present with extensive lesions and systemic disease, which require treatment. Molluscum contagiosum is highly transmissible; therefore, patient education is key in its management. Cryotherapy with liquid nitrogen is the 1st-line treatment.

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Overview

Epidemiology

  • 1% of all diagnosed skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin disorders
  • Usually presents in children < 5 years of age or adolescents
  • Increased incidence in hot, humid climates
  • Slight predominance in boys
  • More common in patients with:
    • HIV
    • Atopic dermatitis Atopic Dermatitis Atopic dermatitis, also known as eczema, is a chronic, relapsing, pruritic, inflammatory skin disease that occurs more frequently in children, although adults can also be affected. The condition is often associated with elevated serum levels of IgE and a personal or family history of atopy. Skin dryness, erythema, oozing, crusting, and lichenification are present. Atopic Dermatitis (Eczema)

Etiology and transmission

  • Molluscum contagiosum virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology: Overview (MCV) is a double-stranded, linear, DNA DNA The molecule DNA is the repository of heritable genetic information. In humans, DNA is contained in 23 chromosome pairs within the nucleus. The molecule provides the basic template for replication of genetic information, RNA transcription, and protein biosynthesis to promote cellular function and survival. DNA Types and Structure poxvirus.
  • Transmission:
    • Exposure to infected individuals ( skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin-to- skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin contact):
      • Sexually transmitted
      • Pre-partum
    • Fomites (e.g., towels, toys, razors)
    • Autoinoculation (scraping)

Pathophysiology

  • Incubation period from 2 weeks to 6 months
  • Virus infects only keratinocytes → localized to epidermis
  • Inhibits innate immunity via antiviral protein production → persistent infection

Histopathology

  • Hyperkeratosis (thickened epidermis)
  • Epidermal proliferation into the dermis
  • Henderson-Paterson bodies: inclusions visible in the keratinocytes of the basal, spinous, and granular layers of the epidermis
Henderson-paterson bodies

Henderson-Paterson bodies:
Characteristic histological features of molluscum contagiosum. Henderson-Paterson bodies are inclusions that are visible in the keratinocytes of the basal, spinous, and granular layers of the epidermis.

Image: “Molluscum Contagiosum 1” by Ed Uthman. License: CC BY 2.0

Clinical Presentation and Diagnosis

Clinical presentation of lesions

  • Usually no systemic symptoms
  • Dermatological features:
    • Shape and color:
      • Dome shaped
      • Pearly papules
      • Flesh colored
      • 2–6 mm in diameter
      • Central umbilication
    • Usually multiple and occur in clusters
    • Rarely associated with pruritus or tenderness
    • Distribution:
      • Children: 
        • Face
        • Trunk
        • Axilla Axilla The axilla is a pyramid-shaped space located between the upper thorax and the arm. The axilla has a base, an apex, and 4 walls (anterior, medial, lateral, posterior). The base of the pyramid is made up of the axillary skin. The apex is the axillary inlet, located between the 1st rib, superior border of the scapula, and clavicle. Axilla and Brachial Plexus
        • Antecubital fossa
        • Popliteal fossa Popliteal fossa The popliteal fossa or the "knee pit" is a diamond-shaped, fat-filled, shallow depression on the posterior aspect of the knee joint. The popliteal fossa is located at the dorsal aspect of the knee and contains an increased number of lymph nodes as well as structures of the neurovascular system that travel from the thigh to the lower leg. Popliteal Fossa
      • Adults: 
        • Anogenital area
        • Abdomen
        • Thighs
      • Palms and soles not involved
  • Immunocompromised individuals may have widespread systemic illness.

Diagnosis

  • Clinical diagnosis is sufficient.
  • Histopathological analysis to confirm diagnosis
  • Lesions in inguinal region → STD STD Sexually transmitted diseases (STDs) are infections that spread either by vaginal intercourse, anal sex, or oral sex. Symptoms and signs may include vaginal discharge, penile discharge, dysuria, skin lesions (e.g., warts, ulcers) on or around the genitals, and pelvic pain. Some infections can lead to infertility and chronic debilitating disease. Overview: Sexually Transmitted Infections panel to rule out accompanying STIs

Management

Treatment

  • No treatment is necessary for healthy individuals as it is a self-limiting disease.
  • Patient education:
    • Complete resolution can take up to 1 year.
    • Avoid sharing towels and sheets, and do not shave across lesions.
    • Cover lesions with a tight bandage.
    • Practice safe sex.
  • Management for cosmetic reasons or to reduce transmission:
    • Physical removal (1st-line therapy):
      • Cryotherapy (liquid nitrogen)
      • Curettage
      • Cantharidin (topical blistering agent to be applied only by a physician)
    • Topical treatment (applied by the patient):
      • Podophyllotoxin
      • Potassium hydroxide/salicylic acid
      • Benzoyl peroxide
      • Tretinoin
      • Topical imiquimod
      • Oral cimetidine
  • Immunocompromised patients:
    • Antiretroviral therapy Antiretroviral therapy Antiretroviral therapy (ART) targets the replication cycle of the human immunodeficiency virus (HIV) and is classified based on the viral enzyme or mechanism that is inhibited. The goal of therapy is to suppress viral replication to reach the outcome of undetected viral load. Anti-HIV Drugs for patients with HIV
    • Interferon-alpha or cidofovir

Prognosis

  • Spontaneous resolution within 1 year in immunocompetent individuals
  • ⅓ of patients may exhibit recurrence.

Complications

  • Cellulitis Cellulitis Cellulitis is a common infection caused by bacteria that affects the dermis and subcutaneous tissue of the skin. It is frequently caused by Staphylococcus aureus and Streptococcus pyogenes. The skin infection presents as an erythematous and edematous area with warmth and tenderness. Cellulitis
  • Conjunctivitis Conjunctivitis Conjunctivitis is a common inflammation of the bulbar and/or palpebral conjunctiva. It can be classified into infectious (mostly viral) and noninfectious conjunctivitis, which includes allergic causes. Patients commonly present with red eyes, increased tearing, burning, foreign body sensation, and photophobia. Conjunctivitis (if present on the eyelids)
  • Abscess
  • Scarring/hypopigmentation after cryotherapy

Differential Diagnosis

  • Basal cell carcinoma Basal cell carcinoma Basal cell carcinoma is the most common skin malignancy. This cancer arises from the basal layer of the epidermis. The lesions most commonly appear on the face as pearly nodules, often with telangiectatic blood vessels and ulceration in elderly individuals. Basal Cell Carcinoma: pearly skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin lesions that may present as ulceration and mimic the lesions of molluscum contagiosum. Basal cell carcinoma Basal cell carcinoma Basal cell carcinoma is the most common skin malignancy. This cancer arises from the basal layer of the epidermis. The lesions most commonly appear on the face as pearly nodules, often with telangiectatic blood vessels and ulceration in elderly individuals. Basal Cell Carcinoma is common in the elderly. Lesions are found in sun-exposed areas. A biopsy may be necessary to differentiate between basal cell carcinoma and molluscum contagiosum.
  • Condyloma acuminatum: flesh-colored pedunculate lesions secondary to HPV HPV Human papillomavirus (HPV) is a nonenveloped, circular, double-stranded DNA virus belonging to the Papillomaviridae family. Humans are the only reservoir, and transmission occurs through close skin-to-skin or sexual contact. Human papillomaviruses infect basal epithelial cells and can affect cell-regulatory proteins to result in cell proliferation. Papillomaviridae: HPV infection. Lesions are mainly present in the anogenital region. Condyloma acuminatum is usually sexually transmitted and can be prevented via vaccination Vaccination Vaccination is the administration of a substance to induce the immune system to develop protection against a disease. Unlike passive immunization, which involves the administration of pre-performed antibodies, active immunization constitutes the administration of a vaccine to stimulate the body to produce its own antibodies. Vaccination. Treatment of lesions is similar to the approach used to treat molluscum contagiosum.
  • Condylomata lata: smooth flesh-like lesions appearing gray or white, located in the vaginal, penile, or anal area, occurring secondary to a syphilis Syphilis Syphilis is a bacterial infection caused by the spirochete Treponema pallidum pallidum (T. p. pallidum), which is usually spread through sexual contact. Syphilis has 4 clinical stages: primary, secondary, latent, and tertiary. Syphilis infection. Condylomata lata is an STI STI Sexually transmitted infections (STIs) are infections that spread either by vaginal intercourse, anal sex, or oral sex. Symptoms and signs may include vaginal discharge, penile discharge, dysuria, skin lesions (e.g., warts, ulcers) on or around the genitals, and pelvic pain. Some infections can lead to infertility and chronic debilitating disease. Overview: Sexually Transmitted Infections and the treatment for primary syphilis Syphilis Syphilis is a bacterial infection caused by the spirochete Treponema pallidum pallidum (T. p. pallidum), which is usually spread through sexual contact. Syphilis has 4 clinical stages: primary, secondary, latent, and tertiary. Syphilis is with antibiotics. Treatment of lesions in condylomata lata is similar to the approach used to treat the lesions in molluscum contagiosum. Patients should be examined for other STIs.
  • Herpes: a painful condition with ulcerating lesions caused by HSV HSV Herpes simplex virus (HSV) is a double-stranded DNA virus belonging to the family Herpesviridae. Herpes simplex virus commonly causes recurrent infections involving the skin and mucosal surfaces, including the mouth, lips, eyes, and genitals. Herpes Simplex Virus 1 & 2 that presents with systemic symptoms. Lesions are more pustular, blistering, and erythematous than those occurring in molluscum contagiosum. Treatment is supportive as infection cannot be completely eradicated. Outbreaks are treated with acyclovir.
  • Varicella zoster: an infection caused by the Varicella zoster virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology: Overview. Flesh-colored lesions with central umbilication present with systemic manifestations of fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever and coryza. The lesions are extremely pruritic. Varicella-zoster infections are self limiting and of short duration, and are typically treated only with supportive care in immunocompetent individuals. Infections can be prevented by vaccination Vaccination Vaccination is the administration of a substance to induce the immune system to develop protection against a disease. Unlike passive immunization, which involves the administration of pre-performed antibodies, active immunization constitutes the administration of a vaccine to stimulate the body to produce its own antibodies. Vaccination.

References

  1. Badri, T., Gandhi, G.R. (2020). Molluscum Contagiosum. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK441898/
  2. Isaacs, S. (2021). Molluscum contagiosum. UpToDate. Retrieved February 15, 2021, from https://www.uptodate.com/contents/molluscum-contagiosum
  3. Coloe, J., Morrell, D.S. (2009). Cantharidin use among pediatric dermatologists in the treatment of molluscum contagiosum. Pediatr Dermatol. 26(4), 405–408. https://pubmed.ncbi.nlm.nih.gov/19689514/ 
  4. Braue, A., Ross, G., Varigos, G., Kelly, H. (2005). Epidemiology and impact of childhood molluscum contagiosum: A case series and critical review of the literature. Pediatr Dermatol. 22(4), 287–294. https://pubmed.ncbi.nlm.nih.gov/16060861/ 
  5. Brown, J., Janniger, C.K., Schwartz, R.A., Silverberg, N.B. (2006). Childhood molluscum contagiosum. Int J Dermatol. 45(2), 93–99. https://pubmed.ncbi.nlm.nih.gov/16445494/

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