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A Purplish Rash on the Instep

ANSWER

The correct answer is lichen planus (choice “d”), an inflammatory condition marked by pathognomic histologic changes such as those described. Hardly on the tip of most primary care providers’ tongues, lichen planus is nonetheless quite commonly occuring.

Tinea pedis (choice “a”) certainly belongs in the differential, but it would be unusual in a woman of this age. The biopsy effectively ruled it out, as it did psoriasis (choice “b”) and contact dermatitis (choice “c”). 

DISCUSSION

Lichen planus (LP) is the prototypical lichenoid interface dermatitis; an inflammatory infiltrate erases the normally well-defined dermoepidermal junction, replacing it with a jagged “sawtooth” band of lymphocytes. In the process, the cells it kills off (keratinocytes) collect at this interface and are incorporated as necrotic keratinocytes into the papillary dermis.

Classically, the recognition of LP is taught with “The Ps.” LP is said to be:

• Papular

• Planar

• Purple

• Polygonal

• Pruritic

• Plaquish

• Penile

• Puzzling

The word “puzzling” may sound nebulous, but it is actually quite useful for dermatology providers. It comes into play whenever a condition stumps us—as in, “What in the world is this?” This puzzlement causes us to at least consider LP.

LP is often papular, and these papules often have flat (planar) tops. The purple color is more striking in lighter-skinned patients. (Almost all inflammatory conditions are more difficult to diagnose in those with darker skin.) More typically, LP lesions are multi-angular or polygonal, often plaquish, and almost invariably pruritic.

LP is common on the legs and/or trunk, favoring the sacral area. It can affect the scalp (being in the differential for hair loss), can cause nail dystrophy, and is relatively common in the mouth, where it presents as a lacy, reticular, slightly erosive process, usually affecting the buccal mucosae. It may be found on the penis, where it is usually confined to the distal shaft and proximal coronal areas.

Like many otherwise benign conditions, LP can present with bullae. In anterior tibial areas, especially on darker-skinned persons, it can be remarkably hypertrophic.

The cause is usually unknown, although certain drugs—especially the antimalarials, gold salts, and penicillamine—have been known to cause LP-like eruptions. It’s been my observation that flares of LP are prompted by stress (certainly present in this patient’s case). LP may have a connection to hepatitis, although no convincing connection has been established.

TREATMENT

This patient’s condition was treated with topical class I corticosteroid ­ointment (halobetasol). For her, having a certain diagnosis was almost as important as successful treatment.

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Joe R. Monroe, MPAS, PA

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dermadiagnosis, dermatology, derm, rash, foot, feet, triamcinolone cream, tolnaftate, cortisone, itching, hypertension, tinea pedis, psoriasis, contact dermatitis, lichen planus
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Joe R. Monroe, MPAS, PA

ANSWER

The correct answer is lichen planus (choice “d”), an inflammatory condition marked by pathognomic histologic changes such as those described. Hardly on the tip of most primary care providers’ tongues, lichen planus is nonetheless quite commonly occuring.

Tinea pedis (choice “a”) certainly belongs in the differential, but it would be unusual in a woman of this age. The biopsy effectively ruled it out, as it did psoriasis (choice “b”) and contact dermatitis (choice “c”). 

DISCUSSION

Lichen planus (LP) is the prototypical lichenoid interface dermatitis; an inflammatory infiltrate erases the normally well-defined dermoepidermal junction, replacing it with a jagged “sawtooth” band of lymphocytes. In the process, the cells it kills off (keratinocytes) collect at this interface and are incorporated as necrotic keratinocytes into the papillary dermis.

Classically, the recognition of LP is taught with “The Ps.” LP is said to be:

• Papular

• Planar

• Purple

• Polygonal

• Pruritic

• Plaquish

• Penile

• Puzzling

The word “puzzling” may sound nebulous, but it is actually quite useful for dermatology providers. It comes into play whenever a condition stumps us—as in, “What in the world is this?” This puzzlement causes us to at least consider LP.

LP is often papular, and these papules often have flat (planar) tops. The purple color is more striking in lighter-skinned patients. (Almost all inflammatory conditions are more difficult to diagnose in those with darker skin.) More typically, LP lesions are multi-angular or polygonal, often plaquish, and almost invariably pruritic.

LP is common on the legs and/or trunk, favoring the sacral area. It can affect the scalp (being in the differential for hair loss), can cause nail dystrophy, and is relatively common in the mouth, where it presents as a lacy, reticular, slightly erosive process, usually affecting the buccal mucosae. It may be found on the penis, where it is usually confined to the distal shaft and proximal coronal areas.

Like many otherwise benign conditions, LP can present with bullae. In anterior tibial areas, especially on darker-skinned persons, it can be remarkably hypertrophic.

The cause is usually unknown, although certain drugs—especially the antimalarials, gold salts, and penicillamine—have been known to cause LP-like eruptions. It’s been my observation that flares of LP are prompted by stress (certainly present in this patient’s case). LP may have a connection to hepatitis, although no convincing connection has been established.

TREATMENT

This patient’s condition was treated with topical class I corticosteroid ­ointment (halobetasol). For her, having a certain diagnosis was almost as important as successful treatment.

ANSWER

The correct answer is lichen planus (choice “d”), an inflammatory condition marked by pathognomic histologic changes such as those described. Hardly on the tip of most primary care providers’ tongues, lichen planus is nonetheless quite commonly occuring.

Tinea pedis (choice “a”) certainly belongs in the differential, but it would be unusual in a woman of this age. The biopsy effectively ruled it out, as it did psoriasis (choice “b”) and contact dermatitis (choice “c”). 

DISCUSSION

Lichen planus (LP) is the prototypical lichenoid interface dermatitis; an inflammatory infiltrate erases the normally well-defined dermoepidermal junction, replacing it with a jagged “sawtooth” band of lymphocytes. In the process, the cells it kills off (keratinocytes) collect at this interface and are incorporated as necrotic keratinocytes into the papillary dermis.

Classically, the recognition of LP is taught with “The Ps.” LP is said to be:

• Papular

• Planar

• Purple

• Polygonal

• Pruritic

• Plaquish

• Penile

• Puzzling

The word “puzzling” may sound nebulous, but it is actually quite useful for dermatology providers. It comes into play whenever a condition stumps us—as in, “What in the world is this?” This puzzlement causes us to at least consider LP.

LP is often papular, and these papules often have flat (planar) tops. The purple color is more striking in lighter-skinned patients. (Almost all inflammatory conditions are more difficult to diagnose in those with darker skin.) More typically, LP lesions are multi-angular or polygonal, often plaquish, and almost invariably pruritic.

LP is common on the legs and/or trunk, favoring the sacral area. It can affect the scalp (being in the differential for hair loss), can cause nail dystrophy, and is relatively common in the mouth, where it presents as a lacy, reticular, slightly erosive process, usually affecting the buccal mucosae. It may be found on the penis, where it is usually confined to the distal shaft and proximal coronal areas.

Like many otherwise benign conditions, LP can present with bullae. In anterior tibial areas, especially on darker-skinned persons, it can be remarkably hypertrophic.

The cause is usually unknown, although certain drugs—especially the antimalarials, gold salts, and penicillamine—have been known to cause LP-like eruptions. It’s been my observation that flares of LP are prompted by stress (certainly present in this patient’s case). LP may have a connection to hepatitis, although no convincing connection has been established.

TREATMENT

This patient’s condition was treated with topical class I corticosteroid ­ointment (halobetasol). For her, having a certain diagnosis was almost as important as successful treatment.

Issue
Clinician Reviews - 23(11)
Issue
Clinician Reviews - 23(11)
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16
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A Purplish Rash on the Instep
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A Purplish Rash on the Instep
Legacy Keywords
dermadiagnosis, dermatology, derm, rash, foot, feet, triamcinolone cream, tolnaftate, cortisone, itching, hypertension, tinea pedis, psoriasis, contact dermatitis, lichen planus
Legacy Keywords
dermadiagnosis, dermatology, derm, rash, foot, feet, triamcinolone cream, tolnaftate, cortisone, itching, hypertension, tinea pedis, psoriasis, contact dermatitis, lichen planus
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Questionnaire Body

 

 

Several months ago, an itchy rash appeared on the foot of this 61-year-old African-American woman. She tried using a variety of OTC and prescription products, including tolnaftate cream, hydrocortisone 1% cream, and triamcinolone cream, but the rash persisted. She reports that the triamcinolone cream did relieve the itching for a few minutes after application, but the symptoms always returned. The rash has gradually grown. The patient, a retired schoolteacher, denies any other skin problems. She does have several relatively minor health problems, including hypertension (well controlled with metoprolol) and mild reactive airway disease (related to a 20-year history of smoking). The rash manifested around the time she was forced to retire in an unforeseen downsizing effort by her school district. As a result, she lost her health care coverage and could not afford private insurance for herself and her husband (neither of whom are old enough to qualify for Medicare). The rash, which covers a roughly 12 × 8–cm area, begins on her left instep and spills onto the lower ankle. It is quite dark, as would be expected in a person with type V skin, but there is a slightly purplish tinge to it. The surface of the affected area is a bit shiny and atrophic, and the margins are well defined and annular. There is almost no scaling, and the rest of the skin on her feet and legs is well within normal limits. A 4-mm punch biopsy is performed on the lesion. The pathology report shows obliteration of the dermoepidermal junction by a bandlike lymphocytic infiltrate in the papillary dermis, associated with vacuolar changes and the accumulation of necrotic keratinocytes in the basal layer.

 

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