Dermatology - Infections Flashcards
Cutaneous Larva Migrans (“Creeping Eruption”)
Caused by: hookworm larva (ancylostoma) from dog & cat excrement.
S/Sx: intense pruritis, erythema & papules at site of entry, serpiginous inflammation about 3 wks post exposure.
Distribution: feet/ankles, butt, back, back of legs
Dx: Hx & PE. CBC might show eosinophilia
DDx: scabies
Lice (Pediculosis)
Caused by: wingless bugs that infect the head, body, or pubis.
S/Sx: Severe pruritis. Possible excoriation. Red puncta from bites. Gray/white nits on hair shaft 1cm from scalp, possible brown specks on skin or clothing.
Dx: Find the lice! Or Wood’s lamp.
DDx: seborrheic derm, impetigo, insect bites
Scabies
Caused by: scabies mite Sarcoptes
S/Sx: Burrows - fine, wavy lines 2-10mm long, often lichenified. Intensely pruritic, esp. at night. May see erythematous papules w/out burrows. Others at home might be infected. Itching continues after tx due to allergic response rather than active infection
Distribution: Hands, arms, feet, gluteal fold, axilla, back of knees
Dx: Burrows = pathognomic. Microscopic exam of burrow scrapings. Hx & PE
DDx: Insect bites, fungus, eczema, folliculitis, impetigo
Molluscum Contagiosum
Caused by: Pox virus in epidermal cells
S/Sx: smooth, hard umbilicated dome with cheesy core. Flesh colored. Up to 15mm, persisting 6-9months. Usually Asx.
Age: Usu. 3-9 yo
Distribution: face, arms, chest, genitals (STI)
Dx: appearance. Biopsy in immunocompromised pts
DDx: Folliculitis, milia, verrucae
Warts (Verrucae vulgaris)
Benign contagious neoplasms caused by HPV
Common wart - dome shaped, rough, gray/yellow/brown/black/skin colored, 2-10mm, Usually asx.
Distribution: hands, knees, genitalia, feet.
Age: peaks at 12-16 yo
Dx: PE - skin lines interrupted & black puncta/pinpoint bleeding when scraped. Biopsy if doesn’t respond to tx.
DDx: squamous cell carcinoma
Others: Filiform (long & narrow), Flat (2-3mm), Plantar (soles of feet), Mosaic (multiple plantar), Condylloma accuminata (genital warts)
Varicella (chickenpox)
Acute, highly contagious vesicular eruption caused by primary infection w/varicella (HHV-3)
S/Sx: Prodrome of malaise, chills, HA, sore throat, anorexia, and dry mouth. Rash comes w/severe pruritis. Lesions are papules, macules, vesicles, pustules, and crusts concomitantly.
Vax: 20% of vax’d get atypical varicella w/maculopapular rash
Distribution: trunk, face, extremities. Sometimes mouth/vagina.
Infectious: 2 days before lesions appear until all crusts are cleared.
Dx: Characteristic rash
DDx: Other viruses, contact derm., zoster, folliculitis, impetigo
Herpes Simplex
Recurrent viral infection by HSV 1 or 2
S/Sx: Vesicles - single or clustered. Malaise, fever, myalgia, HA, regional LA. Prodrome of tingling/discomfort before vesicles that rupture & ulcerate painfully. Heal in 2-6wks. Physical/emotional stress are triggers for recurrence.
Distribution: mouth, eyes, genitals
*Herpetic whitlow: infects distal phalanx w/painful swelling lesion
Dx: Characteristic lesions w/culture of freshly ulcerated lesion. Tzanck smear shows multinucleate giant cells.
DDx: Impetigo, eczema, zoster, hand/foot/mouth dz, pathos stomatitis
Herpes Zoster (shingles)
Latent Varicella (HHV3) infection
S/Sx: Viral outbreak erupts along dermatome - itching for 2-3 days followed by rash.
Distribution: Dermatome, almost never crosses midline
Dx: Pathognomic rash
DDx: before rash onset - MI, pleurisy, migraine. After lesions appear - HSV, primary varicella
Roseola Infantum (Exanthem subium)
Infection of infants/children w/HHV-6 or 7
S/Sx: 3-5 day high fever that subsides as rash appears. Child alert & active. Cervical LA.
Distribution: rash on chest & abdomen
Age: 90%
Hand Foot & Mouth Dz
Febrile disorder from Coxsackie virus
S/Sx: vesicular eruption on skin/mucosa 3-6mm, possible fever, myalgia, LA, abd. pain, no appetite, poor nursing - mouth lesions painful. Heal in 7 days.
Distr.: buccal mucosa, tongue, palms of hands & feet, maybe buttocks or genitals
Age:
Viral exanthems
Catch-all Dx for blood borne viruses causing a skin rash. Usu. w/fever & malaise.
Measles (Rubeola, Morbilli)
Highly communicable paramyxovirus infection
S/Sx: Koplik spots - 1-3mm white/gray/bluish elevations w/erythematous base on buccal/vaginal surface. Rash comes 2-3 days after fever, coryza, conjunctivitis, photophobia & cough, lasts 5-6 days.
Distr.: begins on face, spreading downward.
Dx: Koplik spots/rash. *In countries w/low measles, dx to include 4x or greater increase of IgM/IgG antibody titer
DDx: during rash - scarlet fever, rubella, drugs, roseola, and others.
Rubella (German Measles)
Caused by: RNA Rubella virus
S/Sx: Prodrome - fever & malaise w/faint rash from face down. Rash - pinpoint pink maculopapules, petechiae on soft palate possible. Mild dz.
Distr.: face down, generalized w/in 24hrs
Dx: Characteristic rash & LAD. Only need labs in pregnant women & newborns - rubella IgM using enzyme immunoassay
DDx: measles, scarlet fever, drugs, erythema infectiosum
Cellulitis
Acute bacterial infection of the skin
Causes: usu. S. aureas -> GAS. in kids it can be Hib also. Predispositions include immune compromise & IV drug use.
S/Sx: local inflammation and LA. If systemic fever, chills, tachycardia, HA, hypotension, etc.
Distr.: lower legs in adults. Cheeks, periorbital, head & neck in children.
Dx: Hx & PE. CBC, blood culture if non-responsive to tx.
DDx: DVT, gout, CPPD, septic arthritis, stasis derm., insect bite.
Cutaneous Abscess
Collection of pus under the skin
S/Sx: Painful, tender, indurated & erythematous, 1-3cm or larger. Can come w/cellulitis, lymphangitis, LAD and fever.
Dx: H&P
DDx: hidradenitis suppurativa, ruptured epidermal cysts
