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Rickettsial Diseases
Infectious Disease
| Question | Answer |
|---|---|
| Woods, hikers; macular rash at wrist/ankles then moves up extremities then trunk. After 5 days rash at palms & soles = | RMSF (Rickettsia rickettsii) |
| Target lesion, arthralgia, Bell Palsy | Lyme Disease (Borrelia burgdorferi) |
| Lyme arthritis: 3 disease patterns | 40% intermittent monoarticular / oligoarticular process: involves knee +/- other large joints; 20% pattern of waxing / waning polyarthralgias; 10% inflame synovitis: evolves into erosions & joint destruction |
| Lyme dz: stage 1: | 7-10d post bite; erythema migrans (groin, thigh, axilla); 50% flu-like illness |
| Lyme dz: stage 2: | skin, CNS, MS; HA, stiff neck; cardiac (pericard, block) or neuro (Bell, meningitis, encephalitis) |
| Lyme dz: stage 3: | (months-years later); arthritis, chronic synovitis; CNS: encephalopathy, axonal polyneuropathy, leukoencephalitis |
| Acrodermatitis chronicum atrophicans = | bluish-red discoloration of distal extremitis w/atrophy (in Euro, not US); 2/2 Stage 3 Lyme dz |
| Incidence of arthritis associated with Lyme disease | 70% of untreated Lyme disease pts develop arthritis |
| Human monocytic ehrlichiosis (HME) causative organisms | Ehrlichia chaffeensis and Ehrlichia canis |
| Human granulocytotropic ehrlichiosis (HGE) causative organisms | Anaplasma phagocytophilum and Ehrlichia ewingii |
| Ehrlichiosis organisms are: | Tickborne GN obligate intracellular organisms, exhibiting tropism for either macrophages or granulocytes |
| Major vector for Ehrlichiosis | HME: lone star tick (endemic in SE, mid-Atlantic, & S central US). HE: Ixodes deer tick (same geography as Lyme) |
| RMSF causative organism | Rickettsia rickettsia. Primary vector is Dermacentor andersoni (RM wood tick) in west and Dermacentor variabilis (American dog tick) in east |
| RMSF pathology | Rickettsia multiplies within endothelial cells lining small blood vessels |
| RMSF clinical features | 2-14 day incubation (mean 7 days). Rash, rapid high spiking fever; severe HA; cough, pneumonitis, delirium; possible seizure, HSM, myocarditis, necrotizing vasculitis |
| RMSF rash appears when? | Day 2-7 of fever. Initial lesions faint macules that blanch with pressure => maculopapular => petechial. Wrists / ankles => spread centrally but mostly on palms/soles |
| Lyme pathology | Immune complexes accumulate in joints & attract neutrophils that attack antigen-Ab complexes. Neutrophil enzymes attack joints, erode bone => arthralgias. Borrelia O-antigen => macrophage interleukin-1 => collagenase & prostaglandin |
Created by:
Abarnard
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