Differential Diagnosis > Morphology > Reaction Patterns Expanded > Purpura > Palpable Purpura

Palpable Purpura

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palpable purpura = vasculitis

 

palpable because of inflammation
end stage of "vascular reaction pattern" (wheal = early stage)
think: hmtoggle_plus1         septic vs. hypersensitivity:
septic = distal, sparse (small # of lesions), and asymmetric
hypersensitivity = symmetric bilateral lower extremities

 

 

Septic Vasculitis

distal, sparse (small # of lesions), and asymmetric
thrombosis of vessels
if become generalized, think of superimposed DIC
embolization of organisms

 

hmtoggle_plus1Septic vasculitis organisms:
meningococcemia
gonococcemia
staphylococcemia
pseudomonas (e.g. ecthyma gangrenosum)
subacute bacterial endocarditis

 

 

Hypersensitivity Vasculitis

symmetric bilateral lower extremities; palpable purpura
etiologies: drug, group A beta-hemolytic strep (antecedent URI), collagen vascular disease
clinical ddx: benign pigmented purpura, scurvy, Kaposi's sarcoma  
see leukocytoclastic vasculitis