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The term "leukocytoclastic vasculitis" can be confusing when first learning dermatology because it is often misused to describe more than one thing. Officially it is a histologic description of small vessel vasculitis. But it is often used to describe the clinical presentation of "bilateral lower extremity palpable purpura" in an otherwise healthy patient. In this case using the term "leukocytoclastic vasculitis" implies the clinical diagnosis of "hypersensitivity vasculitis", but people will often just say "LCV".
Hypersensitivity Vasculitis:
| • | AKA necrotizing venulitis |
| • | defined clinically and histologically |
| • | histology of LCV = “pink donuts in the dermis” |
| • | clinically = bilaterally symmetric palpable purpura on LE’s |
etiology top five –
| • | drugs drugs probably account for a minority of LCV (exception: IV streptokinase; 3% of exposed individuals) |
| • | chronic active hepatitis |
| • | malignancy (especially hematologic) |
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| • | scurvy (perifollicular hemorrhage) |
| • | thrombosis (anti-phospholipids, cryoglobulinemia) |
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| • | pathogenesis: immune complexes --> complement (C5a) --> neuts --> fibrinoid necrosis of vessel wall |
| • | the unifying concept here “immune complex disease” (LCV often associated with chronic diseases in which immune complexes form e.g. SLE, IBD, chronic active hepatitis)? |
| • | also several signs and symptoms of necrotizing vasculitis resemble serum sickness (i.e. immune complexes), including fever, myalgias, arthralgias and arthritis |
treatment:
| • | colchicine: dose = 0.6mg BID (ineffective in prospective, randomized trial, but safe) |
systemic involvement (usually skin only, but may include):
| • | peripheral neuropathy with hypoesthesia or paresthesia |
lab work up:
| • | I do not go crazy with lab tests looking for an etiology when there is one episode only of what appears to be "hypersensitivity vasculitis" (e.g. I don't do ANCA, ANA etc...) |
| • | take a good history to rule out the top five etiologies (see above) |
| • | consider lab tests to rule out systemic involvement: CBC, BUN/Cr, UA, ESR, stool Guiac |
Diseases with LCV histology but....
| • | but do not present with bilateral lower extremity palpable purpura |
| • | OR are not vasculitis at all |
LCV seen histologically in:
| • | erythema nodosum leprosum |
| • | cryoglobulinemia (only in mixed cryoglobulinemia) |
histologic features of (but not in fact) vasculitis:
| • | Erythema Marginatum (and Still’s disease) – neutrophils and dust around blood vessels, but no fibrin |
| • | Sweet’s syndrome – neutrophils and dust (diffusely ) but no fibrin |
| • | Livedo Vasculitis – prominent fibrin plus thrombosis (some vessels have fibrin without thrombosis) |
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