What May Resemble Psoriasis?

Pityriasis rosea

Pityriasis rosea is a condition seen in people between the ages of 10-35 years of age. In contrast to psoriasis, it often starts with a solitary large "Herald Patch" before multiple smaller lesions develop. In pityriasis rosea, the lesions are generally thinner with less scale. The face, palms and soles are not usually involved.

Tinea corporis

Tinea corporis is a fungal infection on the body. Red scaly patches may be seen, but unlike psoriasis, the centers of the patches often show clearing. The edges have scaling (which is usually not as thick as in psoriasis) and may also have pustules. A fungal culture is usually positive.

Lichen planus

In psoriasis, there is usually much more scale and the patches are generally larger and red in contrast to lichen planus, which has smaller purple lesions with less scale. In lichen planus, the flexural areas, particularly the wrists, are affected, while in the psoriasis the extensor areas (such as the elbows) are affected.

Secondary syphilis

In secondary syphilis, a generalized rash similar to psoriasis may be seen, however, blood tests for syphilis are usually positive.

Mycosis fungoides

Mycosis fungoides is a T cell lymphoma in the skin. The lesions tend to be chronic, but lack the thick, silvery scales that are seen in psoriasis.

Hand and foot dermatitis

Pustulosis palmaris and plantaris may look similar to dyshidrotic eczema, however, in the latter, blisters rather than pustules (unless there is a secondary infection) are seen on the sides of the fingers, toes, palms and arches of the feet.

Tinea pedis

Tinea pedis is a fungal infection of the soles of the feet that usually starts in the lateral web spaces, then spreads to the soles. Nails may be secondarily infected and look very similar to psoriasis. A fungal culture will usually be positive in this condition. In psoriasis, the scales on the soles are usually thicker and more well defined and the fungal culture is negative.

Seborrheic dermatitis

In seborrheic dermatitis, the scales are usually yellow rather than white and well defined patches are not usually seen. The eyebrows and cheeks next to the nose may be involved, and the elbows and knees (which are commonly involved in psoriasis) are not affected. In psoriasis, the lesions often extend beyond the hair border onto the face or neck.

Fungal infections

In scalp fungal infections, the hair is often broken, hair loss and pustules may be seen and a fungal culture is usually positive.

Lupus erythematosus

In lupus erythematosus, the lesions are usually more purple in colour, the skin may be thinned, scaling is more prominent around the hair follicles and hair loss is common.