LEUKOCYTOCLASTIC VASCULITIS
Many forms
of vasculitis can affect the skin, the most common one being leukocytoclastic
vasculitis. Other forms of vasculitis known to affect the skin as well as other
organ systems include Churg-Strauss vasculitis, Henoch-Schönlein purpura,
Wegener’s granulomatosis, polyarteritis nodosa, and urticarial vasculitis. Leukocytoclastic
vasculitis is by far the most commonly encountered of the cutaneous
vasculitides. The causes and pathomechanisms vary, and diagnosis and treatment
depend on the results of the clinical and histological evaluations.
Clinical
Findings: Leukocytoclastic vasculitis most commonly affects the lower extremity or
dependent areas of the body. For example, this form of vasculitis is most
commonly seen on the legs of ambulatory patients but on the back and buttocks
of bedridden patients. The clinical hallmark of vasculitis is the presence 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 uniform in size, but
they can range from minute to 1 cm or more in diameter. Patients are most
likely to complain of mild itching or no symptoms at all, and the appearance of
the rash is what brings them to see the clinician. Mild constitutional symptoms
are often present, with mild fever, fatigue, and malaise most commonly
reported. Skin-specific symptoms can range from mild pruritus to pain and
tenderness to palpation.
The etiology
of cutaneous leukocytoclastic vasculitis is heterogeneous. The three most
common causes are infections, medications, and idiopathic causes. Almost every
possible infection (bacterial, viral, parasitic, and fungal) has been reported
to be an initiating factor for leukocytoclastic vasculitis. Medications are 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
medication is removed, the vasculitis resolves in approximately 1 month. The
symptoms also cease, often faster than the rash resolves. Postinflammatory
hyperpigmentation with some hemosiderin deposition often is a residual finding
after the lesions have cleared. This resolves slowly over 6 to 12 months.
Pathogenesis:
Leukocytoclastic
vasculitis is a type III hypersensitivity reaction. Soluble antigens are
believed to become complexed with antibodies. As these antigenantibody
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 neutrophils, and continued blood
vessel destruction, leading to the typical cutaneous findings.
Histology:
The
pathology is centered on the blood venules in the dermis. A prominent
neutrophilic infiltrate is present. Degeneration of the neutrophils is always
seen, with nuclear dust; this is termed leukocytoclasis. Fibrinoid
necrosis of the vessel walls is easily seen. Extravasated red blood cells are
seen in the vicinity of the vasculitis. Thrombosis of affected vessel walls is
a secondary finding and is not the primary pathology.
Treatment:
Therapy
is based on the cause of the leukocytoclastic vasculitis. New offending
medications should be withdrawn and replaced with substitutes of a different
class. Infections need to be thoroughly treated. The use of topical
high-potency corticosteroids is helpful in some cases, and oral steroids may be
used in medication-induced leukocytoclastic vasculitis. In cases of
infection-induced vasculitis, prednisone should be reserved until after the
infection has been properly treated. Idiopathic vasculitis is treated with oral steroids, and often
a search for an infection or other cause is undertaken. A thorough history and
physical examination are needed,
as well as some screening laboratory tests. Laboratory testing usually is not
helpful unless the history or review of symptoms points in a particular
direction. If patients are suffering from more than just very mild systemic
symptoms, an evaluation should be done to rule out the more serious forms of
vasculitis.
