Derm E1: Infectious Exanthems -Bacterial, Viral, and Fungal Skin Infxns

THE MOST IMPORTANT SECTION!!!

What is an exanthem?

rash on the outside of the body

What is an enanthem?

rash on the inside of the body

What are bacterial exanthems?

scarlet fever, SSSS, TSS

What causes Scarlet Fever?

Group A Streptococcus (S. pyogenes)

What are the clinical features of Scarlet Fever?

• diffuse erythematous “sandpaper” rash that blanches

• starts in groin/axilla → trunk, spares palms/soles

• circumoral pallor

• strawberry tongue

• pastia lines

What is the tx for Scarlet Fever?

• 1st line

  • Penicillin V

  • Amoxicllin: kids

• 2nd line

  • Cephalosporins

  • Clindamycin

  • Macrolides -Azithromycin

What are complications of Scarlet Fever?

RF, glomerulonephritis, STSS, post strep reactive arthritis, necrotizing fasciitis

What causes Staphylococcal Scalded Skin Syndrome (SSSS)?

exotoxins from S. aureus undergo hematogenous dissemination to the skin; primarily affects children and adolescents

What are the clinical features of SSSS?

• rash following URI

• diffuse skin pain, blanchable erythema

• flaccid bulla/blisters

• absence of mucous membrane involvement

• sheet-like superficial desquamation

What is the pathophysiology of SSSS?

pathogenic toxins- exfoliative toxin A and B; hematogenous spread of toxins stimulates the separation of epidermal keratinocytes and detachment of the superficial epidermis

What are the risk factors for SSSS?

age < 6 yo, impetigo, immunosuppression, impaired renal fxn, DM, staph pneumo, septic arthritis, bacterial conjuntivitis

Would key clinical sign would help dx SSSS?

+Nikolsky sign

What is the tx for SSSS?

• tx like burn pts, hospital admission -isolations, IV fluids

• IV Abx: oxacillin or nafcillin alt. Vanc

• Supportive care

• watch CBC, CMP, UA for sepsis

What causes TSS?

S. Aureus, Group A Strep (S pyogenes)

What are clinical features of TSS?

• initial: diffuse red macular rash (palms/soles), fever, hypotension

• late: pruritic maculopapular rash w/ desquamation of palms/soles

• fatigue, myalgia, GI, Neuro, tachycardia, conjunctival hemorrhage

What is the pathophysiology of TSS?

Toxins (TSS toxin Type 1) and Staph enterotoxin B activate large numbers of T cells → massive cytokine production;

IL-1 causes muscle proteolysis → high fever and myalgias

What are the risk factors for TSS?

tampon usage, surgery, mastitis, burns, sinusitis, osteomyelitis

How is TSS dx according to the CDC guidelines?

Temp >102, hypotension, diffuse macular erythroderma, desquamation, involvement of 3+ organ systems -in absence of any other cause for these sx

How can you dx TSS using labs?

blood cultures, bacterial cultures, inc BUN/Cr, inc CPK, inc LFTs, leukocytosis, thrombocytopenia, anemia

When should you draw the blood culture when testing for infection?

prior to starting the Abx

What is the tx for TSS?

• hospital admission

• treat shock: fluids, vasopressors, surgical debridement

• Empiric Abx: broad -Vancy + Clinda + Zosyn or Cefepime or Carabapenem

What causes folliculitis?

S. Aureus - most common; P. aeruginosa -hot tub

What clinical features are associated with folliculitis?

• superficial: perifollicular papules/pustules w/ erythema ± pruritus

• deep: nodules, furuncles

• hot tub: papules/pustules on trunk and buttocks in bathing suit distribution

What is the tx for folliculitis?

• mild: topical mupirocin, topical Clinda

• moderate/severe: Dicloxacillin, Cephalexin

• MRSA: Bactrim, Clinda

• Hot tub: cipro

What is a furuncle?

infection of the hair follicle in which purulent material extends through the dermis into the subcutaneous tissue

What is a carbuncle?

coalescence of several inflamed follicles into a single inflammatory mass w/ purulent drainage from multiple follicles in the epidermis

What is an abscess?

collection of pus within the dermis and deeper skin tissues

What causes furuncles, carbuncles, and abscesses?

S. aureus -most common

What are the clinical features of a furuncle/carbuncle/abscess?

painful, fluctuant, erythematous nodule ± surrounding cellulitis

What is the tx for a furuncle/carbuncle/abscess?

I&D + Abx (pack if > 5cm); Abx cover for MRSA - Bactrim or Tetracycline

When are Abx not indicated after an I&D?

abscess < 2 cm and individual is healthy

What causes Impetigo and Ecthyma?

S. Aureus or Group A Streptococcus

Who is most likely to get Impetigo or Ecthyma?

children ages 2-5

What is Impetigo?

contagious epidermal infection; honey crusted lesions, “pyoderma”

What is Ecthyma?

ulcerative form of impetigo; extends into the dermis

What are the clinical features of Ecthyma?

“punched-out ulcers” covered w/ yellow crust surrounded by raised violaceous margins

What are the clinical features of non-bullous impetigo?

most common; begins as pustules overlying erythema, lesions break → golden/honey crusts; involve face and extremities; well localized

What are the clinical features of bullous impetigo?

due to S. Aureus toxin A; vesicles enlarge to form flaccid bullae w/ clear yellow fluid → become darker and more turbid → rupture → thin brown crust; only on the trunk

What is the tx for Impetigo?

• localized 1st line: Mupirocin (bactroban) ointment

• extensive: Cephalexin or Doxycycline

What is unique about Erysipelas?

involves upper dermis and superficial lymphatics; clear demarcation of involved tissues

What is unique about cellulitis?

involves the deeper dermis and subcutaneous tissue, spreads more; purulence

What causes Erysipelas and Cellulitis?

S. pyogenes -MCC or S. Aureus

What are the shared clinical features of Erysipelas and Cellulitis?

skin erythema, edema, and warmth; fever

What is the biggest risk factor for developing Erysipelas or Cellulitis?

pre-existing skin infection

What disease is Milian’s ear sign evident in?

Erysipelas

What is the tx for Erysipelas and Cellulitis?

• Outpt: Cephalexin;

  • PCN allergy → Bactrim

• Inpt (septic or immunocompromised):

  • IV Vanc + Cefepime

  • PCN allergy → IV Vanc + levofloxacin

What causes Lymphangitis?

• Immunocompetent: MCC- S. pyogenes and S. aureus

• Immunocompromised: G- organisms

• Animal bite: Pasteurella multocida

• Cat bite: Bartonella henselae

• Fish exposure: Erysipelothrix

What are the clinical features of Lymphangitis?

seen w/ cellulitis, typically due to puncture, erythematous streaking, fever

What is the tx for Lymphangitis?

IV or oral broad spectrum Abx; surgical debridement

How does cutaneous TB present?

variety of presentations: inflammatory papules, verrucous plaques, suppurative nodules, chronic ulcers, other lesions

What causes cutaneous TB?

M. tuberculosis

What are the risk factors for cutaneous TB?

immunocompromised, hx of TB, F > M

How is cutaneous TB transmitted?

direct inoculation of TB into skin, extension into the skin from underlying infective focus, spread to the skin via the bloodstream

What are the clinical features of cutaneous TB?

• painless, shallow ulcers w/ granulomatous base

• Verruocas cutis- painless, violet/red indurated wart like plaques

• scrofuloderma -firm painless, subcutaneous nodules → enlarge and ulcerate → scar

• cutis orificialis

How is cutaneous TB diagnosed?

• PPD

• Acid fact bacilli smear (rapid results)

• Mycobacterial culture -GOLD standard

• skin biopsy: tuberculoid granuloma ± caseating necrosis

What is the tx for cutaneous TB?

• 2 months of intensive therapy

  • Ethambutol + Rifampin + Isoniazid + Pyrazinamide

• Followed by 4 moths of maintenance

  • Isoniazid + Rifampin

What is another name for Leprosy?

Hansen’s disease

What causes Leprosy?

Mycobacterium leprae; spread via droplets

How long is the incubation period for Leprosy?

months to years

What are the risk factors associated with Leprosy?

armadillo exposure, close contact w/ infected, older age, immunosuppression

What are the clinical features of Leprosy?

• hypopigmented or reddish patches

• diminished sensation w/in skin patches

• paresthesisas in hands or feet

• painless wounds or burns on hands/feet

• lumps or swelling on the earlobes or face

• tender, enlarged peripheral nerves

• hair loss

How can you dx Leprosy?

PCR or Acid fast stain

What is the tx for Leprosy?

• Tuberculoid: Dapsone + Rifampin x 1 yr

• Lepromatous: Dapsone + Rifampin + Clofazimine x 2 yrs

What are complications of untreated Leprosy?

nerve damage → paralysis, deformation of hands/feet; corneal ulcers, blindness, saddle nose deformity

What are the predisposing conditions that increase risk of Erythrasma?

warm climates, hyperhidrosis, poor hygiene, obesity, DM

What are the clinical features of Erythrasma?

limited to body folds, Asx or pruritic, duration varies, well demarcated, brown-red or tan patches ± scaling

What color would Erythrasma illuminate as under a Woods lamp?

coral-red florescence

What is the tx for Erythrasma?

• 1st line

  • topical erythromycin or clindamycin

• 2nd

  • topical miconazole or benzoyl peroxide

• Severe: oral Abx

  • clarithromycin

  • erythromycin

What is the cause Meningitis/Meningococcemia?

Neisseria meningitidis

What are the clinical manifestations of Meningitis/Meningococcemia?

• HA, N/V, myalgias

• Triad: sudden onset fever, AMS, nuchal rigidity

• Petechial rash: purpura and ecchymosis

What cutaneous features are associated w/ Meningitis/Meningococcemia?

maculopapular rash on trunk, LE, and mucous membranes → petechiae appear, lesions become purpuric/hemorrhagic, bullae

What is a complications of Meningitis?

purpura fulminans: purpura, ecchymoses, confluent green/black necrosis associated w/ DIC

What is the GOLD standard for dx Meningitis/Meningococcemia?

Blood or CSF culture

What is the tx for Meningitis/ Meningococcemia?

IV Ceftriaxone

What is the cause of Syphilis?

Treponema pallidum -a spirochete

How is Syphilis transmitted?

direct contact w/ an infectious lesion, fetal infection via placenta

What are the clinical features of Primary Syphilis?

painless ulcer or chancre -heal spontaneously, non-tender regional LAD

What are the clinical features of Secondary Syphilis?

diffuse, bilateral, symmetric maculopapular rash +palms/soles, copper brown lesions, Condyloma Lata, regional LAD, cutaneous ulcerations

What are the clinical features of Late stage Syphilis?

gumma, neurosyphilis, AR, AA, aortitis

What is the tx for Syphilis?

PCN G benzathine; Alt: Doxy

-late stage = longer prescription time

What causes Chancroid?

Haemophiles ducreyi

What are the clinical features of a Chancroid?

• erythematous → pustule → ulcer

• LAD → bubo, swollen inflamed lymph node

• painful genital ulcers w/ irregular borders covered by a gray or yellow exudate

What is the tx for a Chancroid?

• 1st line: Azithromycin or Ceftriazone

• Alt: Erythromycin

What is the cause of Cat-Scratch Disease?

Bartonella henselae

What are the clinical features of Cat-Scratch Disease?

erythematous papule/vesicle, regional LAD proximal to lesion, prolonged fever

What are the complications of Cat-Scratch Disease?

visceral organ involvement, ocular manifestations, infection of conjunctiva, neuro sx, encephalopathy, MSK sx

What is the tx for Cat-Scratch Disease?

• 1st line: Azithromycin

• Clarithromycin or Trimethoprim-sulfamethoxazole

What causes Rubella (German Measles)?

Rubella virus

What are the clinical features of Rubella?

low fever, cough LAD, Exanthem: pink or red non-confluent maculopapular rash, face → trunk, spares palms/soles, Forcheimer spots: red macules or petchial spots on the soft palate

What is the tx for Rubella?

supportive care: antipyretics, hydration

What is the cause of Rubeola (measles)?

Rubeola virus

What are the clinical features of Rubeola?

• stage 1: incubation

• stage 2: prodrome - High fever, cough, coryza, conjunctivitis (3 C’s)

• Stage 3: Koplik spots, exanthem: begins at hairline → spreads craniocaudally and centrifugally

• Stage 4: recovery, cough may persist

What is the tx for Rubeola?

supportive, Vitamin A, Ribavirin -high risk pts

What is the most common cause of measle related deaths?

Pneumonia

What is the cause of Roseola Infantum (6th disease)?

Human Herpes virus 6 (HHV-6)

What are the clinical features of Roseola?

acute onset high-fever up to 104 → small rose-pink maculopapular rash, begins on the trunk and spreads, nonpruritic

What is the cause of Hand, Foot, and Mouth Disease?

Coxsackie A16, Coxsackie A6, Enterovirus A71

What are the clinical features of Hand, Foot, and Mouth Disease?

mild fever, reduced appetite, oral lesion w/ halo of redness, painful vesicles, refusal to eat, rash of hands/feet + palms/soles

What is the cause of Erythema Infectiosum (Fifth Disease)?

Parvovirus B19

What are the clinical features of 5th Disease?

fever, HA, nausea → malar rash w/ circumoral pallor, “slapped cheek appearance”, lacy eruption on the trunk, palms/soles spared, aplastic crisis