Concomitant Psoriasis and Allergic Contact Dermatitis: Coexistent Interrelated Clinical Entities

Irritant and allergic contact dermatitis occuring in a patient with psoriasis may clinically appear as a dermatitis, psoriasis (eg, pustular psoriasis) or as an ill-defined subgroup sometimes designated eczematous psoriasis. This subgroup of psoriasis has a clinically heterogenic picture, but retains the chronicity of classical psoriasis. Coexistence of psoriasis and contact dermatitis has prognostic and therapeutic implications for the patient. Allergic contact dermatitis in psoriatics may present itself clinically as psoriasis, and the diagnosis can therefore be missed unless appropriate patch testing is performed. The present study examines the clinical presentation of patients with recognized eczematous psoriasis. It is concluded that the definition of this entity primarily rests on the patient history and response to treatment. The morphology and distribution of the skin lesions are of lesser importance. A missed contact allergy in a psoriasis patient may be one of several reasons why the psoriasis spreads or resists adequate treatment.