PSORIASIS   3A

A 25-year-old woman presents with a complaint of rash that has developed over the past several weeks and seems to be progressing. She describes the involved areas as mildly itchy. On examination, she is noted to have several plaque-like lesions over the extensor surfaces of both upper and lower extremities as well as similar lesions on her scalp. The plaques are erythematous with silvery scales and are sharply marginated.

What are the salient features of this patient’s problem? How do you think through her problem?

Salient features: Progressive rash; mild itching; plaque-like lesions; extensor surfaces of extremities and scalp distribution; sharp margins with silvery scales

How to think through: What are the common skin diseases in the differential diagnosis of this woman’s eruption, and what features about her presentation make psoriasis the most likely diagnosis? (Candidiasis, tinea, and atopic dermatitis are characterized by poorly demarcated lesions and typically present on the extensor surfaces. Candida, in particular, is found in the moist body folds and flexural surfaces. This patient’s lesions are described as mildly pruritic, which is more typical of psoriasis than these alternative diagnoses. The scaly scalp plaques are particularly characteristic of psoriasis.) How does her presentation differ from that of seborrheic dermatitis?

What other manifestations should you explore? (Nail pitting is common in psoriasis and will help confirm your diagnosis. Joint pain and inflammation would raise the possibility of psoriatic arthritis.)

PSORIASIS   3B

What are the essentials of diagnosis and general considerations regarding psoriasis?

Essentials of Diagnosis

Silvery scales on bright red, well-demarcated plaques, usually on the knees, elbows, and scalp

Nail findings include pitting and onycholysis (separation of the nail plate from the bed)

Mild itching (usually)

May be associated with psoriatic arthritis

Patients with psoriasis are at increased risk for metabolic syndrome and lymphoma

Histopathology is not often useful and can be confusing

General Considerations

A common benign, chronic inflammatory skin disease with both a genetic basis and known environmental triggers

Injury or irritation of normal skin tends to induce lesions of psoriasis at the site (Koebner phenomenon)

Psoriasis has several variants; the most common is the plaque type

PSORIASIS   3C

What are the symptoms and signs of psoriasis?

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