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Chapter 35: Skin Diseases of the Legs

Noah Goldfarb; Steven W. Lin

INTRODUCTION TO CHAPTER

The legs are predisposed to dermatoses that are gravity dependent, including stasis dermatitis and vascular conditions such as leukocytoclastic vasculitis, the pigmented purpuric dermatoses, and livedo reticularis. Legs are also the site of frequent trauma and thus are susceptible to conditions that may be induced by trauma including superficial thrombophlebitis, pyoderma gangrenosum, necrobiosis lipoidica, chronic ulcers, and cellulitis. In patients with preexisting vascular conditions affecting the lower extremities, including diabetes mellitus, venous insufficiency, and peripheral vascular disease, traumatic wounds may take longer to heal and may have an increased risk of infection.

APPROACH TO DIAGNOSIS

Skin diseases primarily involving the legs can be broadly categorized into inflammatory conditions, infectious diseases, superficial vascular disorders, neoplastic lesions, and underlying systemic diseases (see Table 35-1). Differentiating between these conditions can usually be done based on an appropriate history and physical examination. Occasionally, dermatitis on the lower extremities may be difficult to distinguish from a cellulitis. Cellulitis of the lower extremities tends be unilaterally, as compared to dermatitis, which usually is bilateral.

Table 35-1.Differential diagnosis for diseases of the legs.
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Table 35-1. Differential diagnosis for diseases of the legs.
Disease Epidemiology History Physical Examination
Inflammatory
Asteatotic dermatitis

Common

M > F

Age: typically >60 years

Pruritus and dry skin

Waxing and waning course

Worse in winter

 Dry, fissured, cracking, mildly scaly and inflamed plaques on bilateral anterior lower legs (Figure 8-3)
Stasis dermatitis

Common

F > M

Age: middle-aged and elderly adults

Asymptomatic or pruritic

Associated with leg swelling

 Erythematous, scaly plaques, may be hyperpigmented, lichenified, or sclerotic on bilateral anterior lower legs, especially medial ankles (Figure 29-1)
Nummular eczema

Common

M > F

Age: Adults

Pruritus

Chronic, waxing, and waning course

Worse in fall and winter

 Round, light pink, scaly, thin, 1-3 cm plaques on legs (Figure 8-11)
Psoriasis vulgaris

Common

M = F. Onset at any age but peaks in 20s and 50s

Asymptomatic to mildly pruritic. Chronic course. May be associated with arthritis

Family history of psoriasis

 Red papules and plaques with silvery, thick, adherent scale, commonly on knees (Figure 9-1)
Erythema nodosum

Uncommon

F > M

Age: 20-40 years

Tender lesions

Variable course

May be associated with fevers and arthralgias

 Indurated, tender, red, deep, poorly defined nodules, usually on bilateral shins (Figure 24-14)
Pyoderma gangrenosum

Rare

F ≥ M

Age: all ages, but typically 30-40 years

Painful. May last months to years

Spontaneous healing may occur

 Initially, a hemorrhagic pustule with surrounding erythema. Later, ulceration with granulation tissue, eschar and purulent material at the base, and a dusky red/purple border (Figure 2-13)
Infectious
Cellulitis

Common

M = F

Age: more common in older adults

Pain, swelling, fever, chills, and malaise

Increased risk in diabetics

 Localized warm, red, tender plaque with ill-defined borders, usually on lower leg (Figure 12-3...

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