Page 127 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 4-42 Rashes

Circulating ANCA
Cytokine receptor
Fc receptor Circulating cytokine
ANCA Circulating cytokines migrate to cytokine receptors
antigen on neutrophil surface.

LEUKOCYTOCLASTIC VASCULITIS
Cytokine primary results in expression of ANCA antigens on
Adhesion molecule neutrophil cell surface.
Many forms of vasculitis can affect the skin, the most Cytokine–cytokine receptor complex
common one being leukocytoclastic vasculitis. Other
forms of vasculitis known to affect the skin as well as Surface ANCA Circulating ANCA–ANCA antigen complex
other organ systems include Churg-Strauss vasculitis, antigen, F(ab’) 2
Henoch-Schönlein purpura, Wegener’s granulomato-
sis, polyarteritis nodosa, and urticarial vasculitis. Leu- ANCA–ANCA antigen complex Neutrophils activated by direct ANCA-F(ab’) 2 binding and by
kocytoclastic vasculitis is by far the most commonly bound to Fc receptor binding of ANCA–ANCA antigen complexes to Fc receptors
encountered of the cutaneous vasculitides. The causes
and pathomechanisms vary, and diagnosis and treat- Adhesion of neutrophils to vascular surface by interaction
ment depend on the results of the clinical and histologi- of adhesion molecules with endothelial adhesion
cal evaluations. molecule receptors
Clinical Findings: Leukocytoclastic vasculitis most Subendothelial migration of neutrophils
commonly affects the lower extremity or dependent
areas of the body. For example, this form of vasculitis Apoptosis of endothelial cell
is most commonly seen on the legs of ambulatory Adhesion molecule–receptor complex
patients but on the back and buttocks of bedridden Endothelial cell
patients. The clinical hallmark of vasculitis is the pres-
ence of palpable purpura. The rash may start as small,
pink, violaceous macules that rapidly develop into red
or purple palpable papules; hence the term palpable
purpura. Most of the lesions of palpable purpura are Process of neutrophil (or monocyte)
uniform in size, but they can range from minute to 1 cm activation by ANCA ultimately results
or more in diameter. Patients are most likely to com- in endothelial cell and neutrophil
plain of mild itching or no symptoms at all, and the apoptosis and necrosis with lytic
appearance of the rash is what brings them to see disruption of vessel wall matrix.
the clinician. Mild constitutional symptoms are often Vessel wall Neutrophil
apoptosis and
present, with mild fever, fatigue, and malaise most necrosis
commonly reported. Skin-specific symptoms can Distribution of specific vasculitis syndromes
range from mild pruritus to pain and tenderness to
palpation. Aorta
The etiology of cutaneous leukocytoclastic vasculitis
is heterogeneous. The three most common causes Large vessel
are infections, medications, and idiopathic causes. vasculitis (giant cell arteritis/ Takayasu arteritis)
Almost every possible infection (bacterial, viral, para-
sitic, and fungal) has been reported to be an initiating Medium-size (polyarteritis
factor for leukocytoclastic vasculitis. Medications are vessel vasculitis nodosa/ Kawasaki disease) Arteries
a common culprit and can easily be overlooked if
a thorough history is not obtained. If the offending
infection is treated properly or the offending medica-
tion is removed, the vasculitis resolves in approximately
1 month. The symptoms also cease, often faster than Arterioles
the rash resolves. Postinflammatory hyperpigmentation Small vessel vasculitis (microscopic polyangiitis/Wegener’s granulomatosis)
with some hemosiderin deposition often is a residual Capillaries Goodpasture’s syndrome
finding after the lesions have cleared. This resolves granulomatosis/Churg-Strauss syndrome
slowly over 6 to 12 months. Venules Microscopic polyangiitis/Wegener’s
Pathogenesis: Leukocytoclastic vasculitis is a type III Henoch-Schönlein purpura Cryoglobulinemia ANCA small vessel vasculitis
hypersensitivity reaction. Soluble antigens are believed Isolated cutaneous leukocytoclastic angiitis
to become complexed with antibodies. As these antigen- Veins
antibody complexes enlarge, they get trapped in the
tiny vasculature of the dependent regions of the body.
There, they can initiate the complement cascade and
cause endothelial cell wall death, recruitment of neu-
trophils, and continued blood vessel destruction,
leading to the typical cutaneous findings.
Histology: The pathology is centered on the blood Treatment: Therapy is based on the cause of the treated. Idiopathic vasculitis is treated with oral ste-
venules in the dermis. A prominent neutrophilic infil- leukocytoclastic vasculitis. New offending medications roids, and often a search for an infection or other cause
trate is present. Degeneration of the neutrophils is should be withdrawn and replaced with substitutes of a is undertaken. A thorough history and physical exami-
always seen, with nuclear dust; this is termed leukocy- different class. Infections need to be thoroughly treated. nation are needed, as well as some screening laboratory
toclasis. Fibrinoid necrosis of the vessel walls is The use of topical high-potency corticosteroids is tests. Laboratory testing usually is not helpful unless
easily seen. Extravasated red blood cells are seen in the helpful in some cases, and oral steroids may be used in the history or review of symptoms points in a particular
vicinity of the vasculitis. Thrombosis of affected vessel medication-induced leukocytoclastic vasculitis. In cases direction. If patients are suffering from more than just
walls is a secondary finding and is not the primary of infection-induced vasculitis, prednisone should be very mild systemic symptoms, an evaluation should be
pathology. reserved until after the infection has been properly done to rule out the more serious forms of vasculitis.

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