Skin Rash Quiz: Lyme Disease and More

SKIN RASH

• Lyme Disease:

  • Causative agent: Borrelia burgdorferi
  • Pathogenesis: Invades skin (then heart, CNS, joints)
  • Manifestations: Erythema migrans (bull's eye rash), Bell’s palsy, arthritis (type 3 hypersensitivity)
  • Diagnosis: Known exposure, clinical presentation, serology
  • Treatment: Doxycycline, Ceftriaxone
  • Prevention: Avoidance of ticks
  • Image: Bull's eye rash

• Erysipelas:

  • Causative agent: Streptococcus pyogenes
  • Pathogenesis: M proteins
  • Manifestations: Dermal pain, fever, rapid spread, skin edema, lymphadenopathy
  • Diagnosis: Catalase (-), Gram (+), Bacitracin
  • Treatment: Penicillin, Erythromycin
  • Image: Raised facial butterfly wing

• Scarlet Fever:

  • Causative agent: Streptococcus pyogenes
  • Pathogenesis: Erythrogenic toxin
  • Manifestations: Fever, trunk + neck extremities, strawberry tongue
  • Diagnosis: (same as above)
  • Treatment: Penicillin, Clindamycin
  • Image: Erythematous rash (sandpaper-like)

TOXIC SHOCK SYNDROME (TSS)

• Staphylococcus aureus (TSST):
  • Predispositions: Skin abscesses, vaginal infections
  • Pathogenesis: Superantigen TSST
  • Manifestations: Acute onset, fever, hypotension, multiorgan failure, myalgia. Temperature 39C or lower, systolic blood pressure 90mmHg or lower, involvement of organ systems
  • Diagnosis: Temp. 39°C <, sys. 90mmHg, diffuse macular erythema, involvement of organ systems
  • Treatment: Cloxacillin, Rifampicin/fusidic acid (faster penetration to inflamed tissues)
  • Image: Generalized maculopapular rash

STAPHYLOCOCCAL SCALDED SKIN SYNDROME (SSS)

• Staphylococcus aureus (pyrogenic exotoxins-exfoliatins):
  • Predispositions: Skin abscesses, vaginal infections
  • Pathogenesis: Desquamation, exfoliatins
  • Manifestations: Neonatal Ritter/Lyell’s syndrome, trunk, neck extremities.
  • Diagnosis: Catalase (+), Gram (+), Coagulase (+), cocci Nikolsky’s sign (+)
  • Treatment: Nafcillin, Oxacillin, Vancomycin (penicillin allergic)
  • Image: Early lesions: pale + flaccid shallow bullae. Severe: scalded lesions.

SECONDARY SYPHILIS

• Treponema pallidum:
  • Predispositions: IV drug abuse (in females)
  • Pathogenesis: Endotoxin
  • Manifestations: Fever, lymphadenopathy, splenomegaly, condylomata lata (anogenital).
  • Diagnosis: Microscopy: exudate from chancre, DF/UV. Serology: Non-specific (VDRL, RPRT), Specific (FTA-ABS, MHA-TP).
  • Treatment: Penicillin, doxycycline, erythromycin
  • Image: early lesions: pale + flaccid shallow bullae. Severe: scalded lesions

OTHER DISEASES

• Rocky Mountain Spotted Fever:

  • Causative agent: Rickettsia rickettsii
  • Pathogenesis: Endotoxin, infects endothelial cells.
  • Manifestations: Anorexia, fever, respiratory symptoms, splenomegaly/lymphadenopathy, shock
  • Diagnosis: Serology
  • Treatment: Doxycycline, Chloramphenicol
  • Prevention: Avoidance of ticks
  • Image: Generalized maculopapular rash

• Epidemic typhus:

  • Causative agent: Rickettsia prowazekii
  • Pathogenesis: Endotoxin, infects vascular endothelium in skin.
  • Manifestations: Fever, arthralgia, lead to severe meningoencephalitis
  • Diagnosis: Serology
  • Treatment: Doxycycline, Chloramphenicol and Delousing by insecticides/Formaldehyde
  • Image: Generalized maculopapular rash

• Scrub Typhus:

  • Causative agent: Orientia tsutsugamushi
  • Pathogenesis: Endotoxin, infects vascular endothelium in skin.
  • Manifestations: Fever, severe headache, lymphadenopathy, splenomegaly, CNS complications. Eschar.
  • Diagnosis: Serology
  • Treatment: Doxycycline and Chloramphenicol
  • Prevention: Avoid exposure to chiggers
  • Image: Macular-papular rash. Eschar (below)

• Other Skin Rashes (Molluscum contagiosum, Rubella, Measles, Roseola):

  • Causative agents, transmission, symptoms, prevention, treatment, and image are all detailed in each skin rash section. Please review the table providing the specific details.

• Viral Hemorrhagic Fevers (Dengue, Yellow Fever):

  • Causes, Pathogenesis, Manifestations, Diagnostics, Treatment, prevention and other important details are listed in each section.

• Ebola Virus Disease, Marburg Virus Disease, Lassa Fever:

  • Causative agent, pathogenesis, manifestations, diagnostics, treatment, and prevention are stated in each description.

• Hantavirus Disease:

  • Causative agent, pathogenesis, stages (Febrile, Hypotensive, Oliguric, Diuretic, Convalescent) and treatment for hantavirus are detailed.

• Norovirus, Rift Valley Fever:

  • Causative agent, pathogenesis, symptoms, diagnosis, treatment, and prevention are included.

• Helminths (Filariasis, Cutaneous Larva Migrans):

  • Causative agents, pathogenesis, manifestations, diagnostics, treatment, and prevention are detailed for each helminth disease.

• River Blindness (Onchocerca volvulus):

  • Causative agent, pathogenesis, manifestations, diagnostics, treatment, and prevention are listed.

• Cercarial Dermatitis/Swimmer's itch:(Schistosomiasis)

  • Causative agent, pathogenesis, manifestations, diagnostics, treatment, and prevention are listed.