More superficial and has the greatest curvature fig 7

more superficial and has the greatest curvature (Fig
7). Trauma or infection may localize ulcers laterally
or in more proximal locations; however, ulcers
above the mid calf or on the foot commonly suggest
another cause 1 (Fig 8). Venous ulcers generally have
borders with irregular margins that are either flat or
with a slight steep elevation. The wound bed of the
venous ulcer tends to be shallow and rarely, if ever,
shows necrotic eschar or exposed tendons. The
presence of these should lead one to an alternative
diagnosis. 33 A yellow, fibrinous bed is seen initially,
but with appropriate therapy it usually evolves into a
healthy granulation tissue base. 1
DIFFERENTIAL DIAGNOSIS
Although most leg ulcers in large series are venous,
the pathogenesis is not venous in all patients. 1 Other
common causes are arterial and neuropathic; howev-
er, the cause of an ulcer is often multifactorial. 100
Arterial ulcers typically appear round or punched
out with a sharply demarcated border. 7,9,86 A fibrous
yellow base or a true necrotic eschar with scant or
408 Valencia et al
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ERMATOL
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Fig 7. Majority of venous ulcers are located over the
medial malleolus. Either or both legs may be affected.
Notice surrounding hyperpigmentation and chronic der-
matitic changes.
Fig 8. Venous ulcer involving the dorsum of the foot. An
arterial origin was initially considered, but distal pulses
were normal, ABI was 1.0, and angiogram showed no arte-
rial disease.

is characterized by an ulcer with a characteristic, pur-
plish-blue, undermined border and a cribriform base.
Two thirds are associated with inflammatory condi-
tions such as inflammatory bowel disease or rheuma-
toid arthritis or with hematologic malignancies. 105
Vasculitis may also cause chronic ulcers. Palpable pur-
pura is the clinical hallmark of leukocytoclastic vas-
culitis; however, a polymorphous eruption that
includes ulcers, necrotic areas, and livedo reticularis
may be seen. Livedo reticularis (reticulated erythema)
may be seen in other conditions, including cryopro-
teinemias and antiphospholipid syndrome. 9,106
Medium-sized vessel and large vessel vasculitis can
also present with venous leg ulceration in combina-
tion with systemic involvement. Connective tissue dis-
eases such as rheumatoid arthritis and systemic lupus
erythematosus may also cause chronic relapsing
ulcers of the lower extremities. 107
Infectious organisms are also implicated in the
formation of acute or chronic lower extremities
ulcers and should be suspected when nonhealing
ulcers do not conform to the usual pattern observed
with more common conditions. Tissue culture, espe-
cially to look for fungal or atypical mycobacterial
infections, will help elucidate the cause. Underlying
diseases that result in immunosuppression predis-
pose patients to such ulcerations. 100
Biopsy of an ulcer is indicated to exclude basal
cell or squamous cell carcinomas, which can occur in
long-standing ulcers. Basal cell carcinomas arising
from venous ulcers appear as exuberant granulation
tissue rolling onto the wound edges. 108