Viral Infections of Skin Flashcards
exogenous source of skin infections
from without. infection at site of lesion. breaks in skin integrity, cuts, pimples, insect bites. mucous membranes
endogenous source of skin infections
from within, disseminated infection. viremia: spread throguh blood and lymph. reactivation from latency
herpesvirus infections
large, enveloped DNA virus. 8 species. secretions and mucous membranes contain infectious herpesvirus when an infected individual has a primary infection or recurrence of a latent infection. Establish latency in neurons or lymphocytes during primary infection. Asymptomatic shedding can occur at any time, and can transmit to naive people.
HSV Type 1
childhood. spread by close contact with active lesions or asymptomatic shedding. lesions on mouth, face, nose, eyes etc. latency in dorsal root ganglia neurons. usually above the waist. treat with acyclovir.
recurrent HSV-1: herpes labialis
cold sores. 20% of seropositive people have recurrent lesions. triggered by fever, UV exposure, stress, hormones, etc. Contagious lesions. treat with acyclovir, zovirax, valtrex, famvir.
HSV Keratitis and corneal scarring
primary infection in eye often from vaginal mucosa at birth. caused by recurrence of HSV 1 or 2. chronic keratitis can lead to corneal scarrring and lost vision. mediated by infiltration of T cells that destroy cornea. may need cornea transplant
Herpetic whitlow
primary HSV-1 or 2 of non-mucosal sites. acquired by direct contact. recurrences at unusual sites: hands, legs, back. treat with acyclovir and derivatives. prevent with gloves
HSV-2: primary genital herpes
extensive vesicular, pustular, or erythematous lesions on penis, labua, anus. Pain itching, fever, malaise, headache. usually below waist. antiviral treatment prevents spread, especially to brain. HSV-1 and 2 double infections are common.
HSV-2: recurrent genital herpes
prodrome: itching, tingling at lesion site a day before outbreak. vesicular lesions appear on penis, labia, anus. contagious lesions, but shedding can be asymptomatic. prophylactic antiviral treatment can reduce recurrences.
varicella-zoster virus
primary infection as chicken pox (varicella). latency in neurons of dorsal root ganglia and remains quiescent for decades. later in life can cause shingles (herpes zoster)
Primary VZV: varicella
aerosol transmission, highly contagious. 1-2 week incubation. fever, malaise precede and accompany rash. latency in dorsal root ganglia neurons. distinctive rash: drops on rose petals. lesions are itchy, vesicular, form scabs that may scar. treat with vaccine (varivax), acyclovir, foscarnet. visceral infections, dissemination to brain, pneumonitis, bacterial infection of lesions. severity increases with age
VZV recurrence: herpes zoster
prodrome: itching, tingling, burning. outbreak along single dermatome. vesicular lesions are extremely painful and puritic. more common in elderly and immunocompromised. treat with acyclovir. complications include keratitis, retinitis, bell’s palsy, posterpetic neuralgia
HZO: herpes zoster opthalmicus
30% of zoster outbreaks affect the face. zoster in eye can destroy retina leading to blindness. all tissues of the eye can be infected and damaged during HZO. long lasting pain common. treat aggressively
VZV vaccines
live, attenuated virus. varivax to prevent varicella. zostavax to prevent zoster. zostavax is 14 times higher dose than varivax. both are recommended
epstein barr virus: primary infectious mononucleosis
B cells and epithelia of oropharynx infection. restricted to humans. childhood infections are often asymptomatic. older teens have Mono.
EBV recurrences
latent in a small fraction of B cells. immune surveillance suppresses EBV. recurrences are linked to B cell cancers, especially in the immunocompromised
oral hairy leukoplakia
epithelial overgrowth caused by EBV. nonpainful hairy or feathery lesions on the tongue or buccal mucosa. associated with HIV infection, transplantation, chemo, etc
cytomegalovirus: primary infection
usually asymptomatic and acquired in childhood. similar to mono caused by EBV. lack of sore throat and presence of petechial rash and jaundice differentiate from EBV.
roseola: exanthem subitum
caused by HHV6b and HHV7. infect CD4+ T cells, site of latency. transmitted in saliva. 3 day illness of high fever, followed by faint rash on the trunk. many infants are mistakenly given antibiotics for a suspected infection, and the rash is attributed to a drug allergy
kaposi’s sarcoma herpesvirus: KSHV, HHV8
KSHV prevalent in african, mediterranean, homo populations. evidence for sexual transmission. found in B cells and endothelial cells. Recurrences linked to cancers associated with KSHV. kaposi’s sarcoma, body cavity based lymphomas, castleman’s disease, hyperplastic lympadenopathy
coxsackie virus
large family of small, naked ssRNA viruses (Enteroviridae)
includes poliovirus and many others that cause GI infections, neuromuscular diseases, and encephalitis and meningitis
skin manifestations of coxsackie virus
herpangina: throat infection causes red ringed blisters and ulcers on tonsils and soft palate. Hemorrhagic conjunctivitis: begins as eye pain, then red, watery eyes with swelling, light sensitivity, and blurred vision.
hand foot and mouth disease
painful red blisters in the throat, tongue, gums, hard palate, inside of the cheeks, and the palms of the hands and soles of the feet. common in preschool aged children and their parents. transmission: highly contagious, spread on hands and surfaces contaminated with saliva and feces. aerosol spread. no treatment
human papilloma virus HPV
small, naked DNA virus. HPV infects skin, genitals, cervix, anus, and mucosa. spread by direct contact. treat with chemical or surgical removal. gardasil: vaccine for young women and men. differentiate from lesions caused by molluscum contagiosum virus
molluscum contagiosum virus
lack of inflamation, pearly vesicles. large, enveloped DNA virus. lesions are umbilicated. occur anywhere on body, and genitals in adults. single giant molluscum may occur. lesions rarely on palms, soles, mucosa, face, eyes. skin-skin contact or fomite transmission. treat with surgery, crytotherapy, or chemicals. topical treatment with cidofovir is promising
monkey pox
indistinguishable from smallpox. 10-15% fatality. endemic to west and central africa. squirrels are the natural host, disease occurs in humans and monkeys. transmission via direct contact, aerosol, ingestion, needles, person to person
variola virus (smallpox)
fever, severe aching pains and prostration, 2-3 days later an umbilicated papular rash over face and extremities. papular, vesicular then pustular rash. scabs leave pitted scars.
variolation evolved into vaccination
variola virus and other poxviruses were blended to create the modern vaccine strain: vaccinia virus
vaccinia adverse vaccine reactions
live vaccine. auto-innoculuation from arm to eyes, generalized vaccinia, virus disseminates through the body, excema vaccinatum: contraindicated with anyone with eczeema. progressive vaccinia: vaccinia necrosum or gangrenosum. in immunocompromised. treat with VIG or cidofovir
measles virus
paramyxovirus. enveloped, negative strand RNA. contagious during incubation. cough, conjunctivitis, fever, rash. Koplik’s spots: small red spots with bluish centers.
rubella virus
togavirus, enveloped positive strand RNA. respiratory virus, aersosol spread. macuopapular rash, lymphadenopathy, arthralgia. congenital infections are severe. prevent with MMR vaccine
