Dermatology Lecture 4: Viral Skin Infections

Viral Skin Infections

• There are four main viral skin infections: warts, molluscum contagiosum, herpes simplex, and chicken pox and herpes zoster caused by varicella zoster virus (VZV).

Warts (Verrucae)

• Caused by human papilloma virus (HPV)
• Involve both skin and mucous membranes
• Mode of infection: direct or indirect contact with infected patient's things
• Incubation period: 1-6 months
• Clinical picture:
  • Asymptomatic skin-colored papules with rough, mammillated surface
  • May take filiform or digitate shapes
• Types of warts:
  • Common warts (Verruca vulgaris)
  • Plane warts (Verruca plana)
  • Plantar warts (Verruca plantaris)
  • Genital warts (Condyloma accuminata)

Complications of HPV Infection

• Infectious to patient and others
• Periungual warts can cause nail dystrophy and destruction
• Painful plantar warts interfere with walking and sporting activities
• Oncogenicity; predispose to cervical carcinoma

Treatment of Warts

• A. Destructive Therapy:
  • Electrocautery
  • Cryosurgery
  • Chemical cautery
  • Lasers
• B. Topical treatment:
  • Salicylic acid ointment
  • Lactic acid
  • Combination of salicylic acid and lactic acid
• Immunotherapy may be combined with destructive methods in refractory cases
• Oral administration of acitretin or isotretinoin in refractory cases
• HPV vaccination is highly effective and is now approved in more than 100 countries for the immunization of prepubertal girls and boys

Molluscum Contagiosum

• Causative organism: Pox virus
• Mode of infection: direct or indirect contact
• Incubation period: 2-6 weeks
• Clinical picture:
  • Shiny, pearly white, dome-shaped papules with a smooth surface and central umbilication
  • Involves non-genital skin or genital skin (STD)
• Treatment:
  • Electrocautery
  • Cryotherapy
  • Laser treatment
  • Topical treatment

Herpes Simplex

• Causative organism: Herpes simplex virus (HSV)
• Mode of infection: direct or indirect contact
• Incubation period: 2-6 weeks
• Clinical picture:
  • Localized blistering
• Treatment:
  • Oral antiviral medications: acyclovir, valacyclovir, and famcyclovir
  • Intravenous acyclovir for severe cases
• Antiviral drugs cannot eradicate the virus from its resting stage within the nerve cells, but can shorten and prevent attacks

Varicella-Zoster Virus (VZV)

• Primary infection: Chickenpox (varicella)
• Mode of transmission: airborne respiratory droplets or through direct contact with the fluid from the open sores
• Clinical picture:
  • Fever, flu-like symptoms, then vesicular rash involving the whole body
  • Complications: secondary bacterial infection, lesions may heal with scarring, central nervous system complications
• Treatment:
  • Symptomatic therapy is usually all that is required
  • Oral acyclovir in people older than 12 years, and in immunocompromised patients
  • Vaccination with live attenuated varicella vaccine is available and recommended especially for immunocompromised patients and non-immune adult females
• Herpes Zoster:
  • Reactivation of VZV in dorsal root ganglia nerve cells
  • Triggering factors: pressure on the nerve roots, spinal surgery, fever, malignancy
  • Clinical picture: unilateral groups of vesicles on erythematous and edematous base, along distribution of one or more sensory nerves
  • Complications: secondary infection, eye complications, post-herpetic neuralgia