Viral Diseases of the Skin

• Herpes Virus is an intranucleuar DNA virus, which is characterized by changes in the nuclei and the presence of inclusion bodies
• Herpesvirus Zoster-Varicella
  • Varicella: chicken pox
    • Ancantholytic vesicles
    • Mild, disseminated vesicular eruptions that are transient
    • High fever is often present.
    • If contract for the first time as an adult: increased risk of encephalitis, and viral pneumonia
  • Varicella will become systemic, but will eventually have the symptoms reside. Many years later in life there may be a recurrence in a single dermatone!
    • The virus survived in a peripheral sensory nerve and results in zoster (shingles)
    • Normally only one dermatone is effected, but can be in one or two other spots. If the recurrence is widespread the patient is likely immunocompromised with leukemia or lymphoma
    • A person with Zoster is EXTREMELY INFECTIOUS! If a speaker with zoster came to speak to us (and people were sitting in the front half of the classroom) they would be infected.
• Herpes Simplex Virus
  • Lesions are common at mucocutaneous junctions (lip, genital labium)
  • Are contracted by direct contact with affected individual
  • Recurrence usually preceeded by systemic stress or local injury (ex: first exposure to cold of the winter)
  • Results in “Fever Blisters” which are very painful. Often are treated with a topical ointment that kills the peripheral nerve
    • If the infection is near the eye, it may involve the cornea and lead to blindness.
    • Hutchinson’s sign: if the tip of the nose is involved, corneal infection sis likely as the tip of the nose Is innervated by the _____________ which also innervates the eye.
      • Ans: nasociliary branch of the ophthalmic nerve
  • Has social implications, and also risks in delivery of child
    • If a women has genital herpes and delivers the child vaginally, of those infected 50% will die, and the other 50% will have a mental sequela (mental retardation). This individuals must have a C section.
  • Type I and Type 2
    • It was generally understood that type I was always found above the navel (oral) and type 2 was always found below the navel (genital). But then came the 60s, and everything got “topsy turvy”
    • Today: 2/3 of type I is above the navel and type 2 is below.
    • Type 2 is more severe.

Verruca vulgaris (the common wart)

• Is a benign papilloma caused by certain strains of HPV (within the papovaviridae family), different from those related to gynecologic neoplasms
• They usually have sharp tops.
  • Condyloma accuminatum is a form of the common wart found in the perineal region. It has a rounded top.
     
  • Remember that papillomas are warts. Condylomas are warts in the genital region.

• Important to consider the possibility of the patient having secondary syphilis, where skin lesions, termed condylomata lata, look similar but have flat tops.

• Is usually a mild, self-limited disease. Your main job as a physician is to recognize the disease and reassure patients that they will be fine
• Involves the development of fine, scaly patches with a viral etiology (the specific virus was not mentioned). These lesions may resemble those in secondary syphilis.
• These patches usually occur in multiple dermatomes simulatenously, and disappear over several weeks to months.

• It is characterized by the development of a “herald patch”
  • This is seen a week or 10 days before the lesions appear in other areas.
  • If a herald patch is not seen, it is important to rule out secondary syphilis.
    • RPR or VDRL for syphilis screening; FTA for confirmation.

     

• Pox-virus diseases
  • Are intracellular dsDNA viruses. They produce eosinophilc inclusion bodies within the cytoplasm of infected cells, termed Guarnieri bodies.
  • Smallpox (variola)
    • Although smallpox has largely been eradicated due to global vaccination efforts, it is important to know it in case it is used in biological warfare.
    • Variola infection involved formation of hard pustules (pus-filled) rather than vesicles (fluid-filled). These tend to occur on the face and can occupy large surface areas, severely mangling people.
    • If the pustules occur in mucous membranes, patients can cough out the virus and transmit it to others.
  • Vaccinia
    • The lesions resemble smallpox lesions, but are less severe.
    • Is used to immunize against variola
  • Molluscum Contagiosum
    • Is caused by Molluscum Contagiosum virus, which infects epithelial cells and causes localized disease that self-resolves in a few months to years.
    • Causes small, exophitic (sp?; means above the plane of the skin), wart-like papules with punctuate centers. They are usually ½ cm across.
    • Can be transmitted by sexual contact.
      • If you see a kid with molluscum contagiosum in the genital area, it might be wise to rule out sexual abuse.
    • The papules are filled with swollen, virus infected cells, containing eosinophilc inclusion bodies known as Henderson-Patterson bodies (aka Molluscum bodies). You can actually see them with the naked eye.
  • Animal pox-viruses
    • Cows (cowpox virus)
    • Sheep (orf virus)
    • Animal virus infections are usually recognized in areas where they are prevalent. I.e. a NYC physician probably won’t recognize an orf virus infection because not too many sheep are running around NYC.
    • Animal viruses can cause highly localized occupational infections (usually of the finger).
  • Rubeola (measles)
    • Caused by Measles virus, a negative sense ssRNA virus from the Paramyxoviridae family
    • Characterized by Koplik’s spots in the oral cavity (see below)
    • Characterized by bright red (fire engine red) patches especially near the parotid gland. These fire engine red spots are known as a morbilliform rash.
    • Vaccine: MMR

    
     

  • Rubella (German measles)
    • Caused by Rubella virus, a positive sense, ssRNA virus from the Togaviridae family
    • Is subclinical in adults but Is very teratogenic to neonates
    • Vaccine: MMR

Intraepidermal Bullous Disease

• Remember that a bulla is a fluid filled vesicle > 1 cm in diameter
• Pemphigus Vulgaris
  • An acantholytic disorder characterized by formation of several intraepidermal bullae
    • Acantholysis: separation of epidermal cells one from the other; cells appear to float within extracellular fluid.
  • Lesions often start in the oral mucosa. There can be extensive skin involvement.
  • The roof of the blister is often ripped off. As a result, the lesions in the oral mucosa don’t really look like blisters but like edema.
    • Why is the roof ripped off? Because the stratum corneum is a bad roof. Thus, the lesions tend to rupture.
  • It is the result of a Type II hypersensitivity reaction (antibodies are produced against a fixed bodily tissue)
    • The oral mucosa has few desmosomes. Instead, cells are fixed together by intercellular cement substance.
    • Autoimmune antibodies are made against the intercellular cement substance, and are deposited in the stratum spinosum. Cell lysis occurs because epidermal cells are stimulated to produce lytic enzymes, not due to any complement or antibody mediated lysis.
  • Can be detected by immunological assays.
    • We can directly assay the antibody to intercellular cement substance from a direct biopsy of the patients skin, or oral mucosa.
    • We can also assay this indirectly by applying the patient’s serum to a biopsy of animal epithelium and applying a fluorescent marker. 

Subepidermal Bullous Lesions

• Bullous Pemphigoid
  • A disease of the elderly (was thought to be a marker of internal cancer, but it is now known to be associated with age)
  • Presents as a sub-epidermal fluid-filled bulla or vesicle.
    • These bullae do not rupture, as with Pemphigus vulgaris. Why? Because the roof of the blister is the entire stratum malphigii, which is a good roof, unlike the stratum corneum.
  • Is a type II hypersensitivity reaction, with autoimmune antibodies (IgG or IgM) against the basement membrane.
  • These autoantibodies can be identified by immunofluorescence by direct and indirect methods as with pemphigus vulgaris.
  • The bulla forms as a result of a complex process involving complement, antibodies, mast cells, and primarily eosinophils.

  

****Note the differences between Bullous pemphigoid and Pemphigus vulgaris

Pemphigus Vulgaris – bullae rupture, intraepidermal bullae, antibodies against cement substance

Bullous pemphigoid – bullae do not rupture, subepidermal bullae, antibodies against basement membrane

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