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Dermatology
Rickettsial Diseases
Built from Dermatology, 5th Edition
What’s inside
14 sections · 87 slides
Overview
- What this deck covers
Classification and history
What rickettsial organisms are, and how each disease was discovered
- What rickettsial diseases are
- Which cells each genus attacks
- Why the target cell matters
- How the field began
- Epidemic typhus changed the course of history
Epidemiology and transmission
How the vectors keep the organisms circulating, and where each disease occurs
- How spotted fever bacteria persist in nature
- The three main US disease-carrying ticks
- Season and geography follow the vector
- Spotted fever cases across the US, by state
- Typhus group bacteria spread differently
- Why louse-borne typhus can re-explode into epidemics
- How the eschar-forming diseases differ from typhus
- Where each rickettsial disease occurs and how it spreads
- Epidemiology of rickettsial and related infections
- Epidemiology of rickettsial and related infections (continued)
- Epidemiology of rickettsial and related infections (continued)
- Epidemiology of rickettsial and related infections (continued)
- Epidemiology of rickettsial and related infections (continued)
- Epidemiology of rickettsial and related infections (continued)
- Epidemiology of rickettsial and related infections (continued)
- Epidemiology of rickettsial and related infections (continued)
- Epidemiology of rickettsial and related infections (continued)
- Epidemiology of rickettsial and related infections (continued)
- Epidemiology of rickettsial and related infections (continued)
- Epidemiology of rickettsial and related infections (continued)
- Epidemiology of rickettsial and related infections (continued)
- Epidemiology of rickettsial and related infections (continued)
- Epidemiology of rickettsial and related infections (continued)
- Epidemiology of rickettsial and related infections (continued)
- How US tick ranges have expanded
Pathogenesis
How the bacteria enter, spread, and injure blood vessels
- How rickettsiae invade and spread through endothelium
- Two ways of injuring the same blood vessel lining
- The core problem: leaky blood vessels
- How the body eventually clears the infection
Clinical course
The typical systemic illness, its laboratory findings, and its risk of death
- The typical early illness
- Laboratory findings and how severe disease progresses
- 25%
- Why delay is the real danger
Shared cutaneous features
The eschar and the evolving rash that many spotted fevers and typhus have in common
- The eschar: a scar left by the bite itself
- How the rash evolves as blood vessels are injured
- Where the rash starts, and where it spreads
- Early rash on the wrists and ankles
- Petechiae on the palms - a later, more severe sign
- Petechiae within a spreading, patterned rash
- Retiform purpura in severe disease
Rocky Mountain spotted fever and related diseases
The classic spotted fever, and the two most common travel-related rickettsioses
- Rocky Mountain spotted fever: the classic course
- Two related, milder eschar diseases
- Eschar of African tick bite fever
- A trap for the diagnosis: serologic cross-reactivity
- Rickettsialpox: an urban, mite-borne rickettsiosis
- Rickettsialpox: eschar and scattered papules
Pathology
What a skin biopsy shows under the microscope
- What a biopsy of a rash lesion shows
- Vessel inflammation under the microscope
Diagnosis and differential diagnosis
Why treatment starts before any test result, and what else can look similar
- Treat first, confirm later
- The clinical decision pathway for suspected rickettsiosis
- Blood tests are often falsely negative early
- Seeing the bacteria directly in tissue
- What else it can look like before the rash appears
- What else it can look like once the rash appears
- What a vesicular rash or eschar can mimic
Treatment
Why doxycycline is the answer for nearly every rickettsial illness
- Doxycycline is first-line for virtually everyone
- Choosing an antibiotic
- Treatment of rickettsial and related diseases
- When alternatives are used - and when they should not be
Scrub typhus
A distinct mite-borne organism, common across rural Asia and the Pacific
- A different organism with an ancient description
- A major, under-recognised global burden
- How scrub typhus presents
- Treatment, and an emerging resistance concern
Human ehrlichioses
Bacteria that hide inside white blood cells, spread by the lone star tick
- A disease recognised only in 1987
- Vector, reservoir, and a shifting range
- How HME presents, and how severe it can be
- Skin findings occur in about a third of patients
- Cutaneous manifestations of human monocytic ehrlichiosis
- Diagnosing and treating ehrlichiosis
Human granulocytic anaplasmosis
A close relative of ehrlichiosis, sharing its tick vector with Lyme disease
- Anaplasma phagocytophilum and HGA
- How HGA differs clinically from HME
Q fever
A hardy, macrophage-loving organism spread mainly by inhalation, not a bite
- Coxiella burnetii: a tough, airborne organism
- How Q fever presents
- What to remember: the shared framework
- What to remember: clinical practice
- References
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- Dermatology, 5th Edition (2-Volume Set)