There are few cutaneous conditions limited to, or particularly characteristic of the thighs; however, eczema and psoriasis commonly appear in this location. The intertriginous inner surfaces of the thighs are subject to heat, moisture, and the friction of undergarments; consequently, many of the resultant dermatoses of this region are considered in Axillary and Inguinal Creases.

The knees and flexor creases of the leg demonstrate localized plaques analogous to those that are found on the elbows and flexor creases of the arms i.e., psoriasis, lichen simplex chronicus, and atopic dermatitis (see Arms).

In contrast, the lower legs have a unique variety of dermatoses that are influenced by such factors as vascular abnormalities that may result in edema, stasis dermatitis, purpura, vasculitis, and ulcerations. Purpuric lesions can be a sign or symptom of other vascular disorders such as a coagulopathy or vasculopathy and may serve as clues to a systemic disease such as systemic lupus erythematosus. Purpuric skin is purple, violaceous, or dark red in color and it does not blanch because blood is present outside the vessel walls. In contrast, erythema that is red in color blanches on compression because blood remains within the vessels.

Red, pinpoint macules (petechiae) or bruises (ecchymoses) are seen most often on dependent areas (i.e., lower legs and ankles and the buttocks in bedridden patients).
Older lesions generally become purple and then turn brown as hemosiderin forms.

Atrophic and ulcerative conditions such as necrobiosis lipoidica, diabetic dermopathy, and pyoderma gangrenosum, as well as various panniculitides such as erythema nodosum, tend to target the thighs and lower legs.

Both upper and lower legs are prone to certain benign neoplasms, namely, dermatofibromas, various melanocytic nevi, and seborrheic keratoses, whereas the more sun-exposed lower legs also tend to develop actinic keratoses, squamous cell carcinomas, as well as melanomas, in susceptible individuals.


Nummular Eczema

Distinguishing Features

  • Itchy, coin-shaped, scaly, eczematous plaques that tend to occur in clusters (Fig. 18-1)

  • Appear mainly on the legs; less commonly, they occur on the arms and trunk, particularly in children

  • Healing or resolving lesions often display postinflammatory hyperpigmentation, particularly in people of color (Fig. 18-2)

Prurigo Nodularis

Distinguishing Features

  • Lesions are reddish, brown, or very darkly hyperpigmented, dome-shaped papules or nodules 1 to 3 cm in diameter (Figs. 18-3 and 18-4)

  • Symmetrically distributed, most commonly appear on the pretibial shafts, less commonly on the extensor areas of the arms

  • They are often crusted or excoriated—pruritus may be intense and lead to vigorous scratching and sometimes secondary infection and can also lead to significant emotional stress and depression

  • Healing results in significant postinflammatory hyperpigmentation

Figure 18-3 Prurigo nodularis.

Scaly, crusted, intensely pruritic nodules in this atopic adult.

Figure 18-4 Prurigo nodularis.

Multiple excoriated, nodules with marked postinflammatory hyperpigmentation.


Distinguishing Features

  • Whitish scale

Asteatotic Eczema

Distinguishing Features

  • Scaly, erythematous eruption

  • Early on, the affected skin feels and looks dry; subsequently, an inflammatory dermatitis may evolve

  • Seasonal recurrences during dry winter months

  • Because the skin often resembles the surface of a cracked porcelain vase, it is often referred to as erythema craquelé. It is also likened to the appearance of a dry riverbed (Fig. 18-5)

Figure 18-5 Asteatotic eczema, erythema craquelé.

Also known as winter’s itch, the skin resembles the surface of a cracked porcelain vase.

Ichthyosis Vulgaris

Distinguishing Features

  • Symmetric scaling of the skin, which varies from barely visible roughness and dryness to thick horny plates

  • Lesions are most apparent on the shins, resembling fine fish scales (Fig. 18-6)

    Figure 18-6 Ichthyosis vulgaris.

    Resembling fish scales.

    (Image courtesy of Robert I. Rudolph, MD.)

    Figure 18-7 Ichthyosis vulgaris.

    Note characteristic sparing of the popliteal fossa.

  • Sparing of the flexural folds (e.g., antecubital and popliteal fossae) is an important diagnostic feature (Fig. 18-7)

  • Scales are small, fine, irregular, and polygonal in shape, often curling up at the edges to give the skin a rough feel

  • Usually starts in the first year of life, progresses until puberty, then usually improves with age and sun exposure

Tinea Corporis

Distinguishing Features

  • Lesions may be characteristically annular, with peripheral enlargement and central clearing; however, less well-defined patches, papules, or scaly plaques tend to occur on the legs (Fig. 18-8)

  • Lesions are single or multiple

  • If multiple lesions are present, their distribution is typically asymmetric

    Figure 18-8 Tinea corporis (“incognito”), KOH positive.

    This patient was initially treated with topical steroids for what was initially thought to be an eczematous eruption.

  • May be pruritic or asymptomatic

  • Majocchi granuloma may result when inappropriate therapy, such as topical steroids, or shaving drives the fungi deeper into hair follicles



Distinguishing Features

  • Superficial, small, red, relatively asymptomatic papules and/or pustules (Fig. 18-10), often in a grid-like pattern

Figure 18-9 Localized plaque psoriasis.

Here there are thick hypertrophic plaques on this patient’s legs.

Lichen Planus

Figure 18-10 Folliculitis.

Note superficial, small red papules with emerging hairs in this young woman who shaves her legs.

Distinguishing Features

Lesions are pruritic, planar, purple, polygonal, pleomorphic, papules, or plaques that heal with postinflammatory hyperpigmentation.

  • The presence of Wickham striae, characteristic white streaks on the surface of lesions, and/or the Köebner phenomenon in which new LP lesions appear at sites of scratching (see also Figs. 13-23 and 13-24)

Clinical Variants: Hypertrophic Lichen Planus

  • Often pruritic, papules or plaques and nodules

  • Chronic, and tend to heal with residual very dark hyperpigmentation (Fig. 18-11)

Erythema Nodosum

Distinguishing Features

  • Lesions begin as bright red, deep, extremely tender nodules (Fig. 18-12)

  • Tends to occur in a bilateral distribution on the anterior shins, thighs, knees, and arms

    Figure 18-12 Erythema nodosum, acute.

    These tender, red nodules appeared after this patient began taking an oral contraceptive.

    Figure 18-13 Erythema nodosum, healing.

    Resolving “contusiform” lesions are present in this patient.

    (Image courtesy of Robert I. Rudolph, MD.)

  • During resolution, lesions become dark brown, violaceous, or bruise-like macules (“contusiform”) (Fig. 18-13)

  • Malaise, fever, arthralgias, and periarticular swelling of the knees and ankles may accompany the panniculitis

  • Other symptoms may also be present, depending on the cause of EN

  • Spontaneous resolution of lesions occurs in 3 to 6 weeks, regardless of the underlying cause

  • Generally, EN indicates a better prognosis in patients who have sarcoidosis

Nodular Vasculitis

Distinguishing Features

  • Crops of small, tender, erythematous nodules may be observed

  • Both nodular vasculitis and erythema induratum are most often seen in females

  • The lower extremities are the most common sites for lesions to arise—often the calves. However, the shins (Fig. 18-14) and ankles also are sometimes involved

  • Lesions ulcerate, resulting in permanent atrophy scarring and hyperpigmentation

  • The nodules have a chronic, recurrent course

Jan 8, 2023 | Posted by in Dermatology | Comments Off on Legs

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