Psoriasis is a common problem that tends to first appear in the late teens and 50s, and to wax and wane in severity; about 2% of the population is affected. The cause of this multisystem, inflammatory condition is not certain but there is a genetic predisposition and certain triggers such as stress, injury, streptococcal infections, excess alcohol, smoking and some medications, for example, ß-blockers, lithium, anti-malarials and NSAIDs.
Plaque psoriasis is a common mode of presentation, with scaly, red, single or multiple, circular or oval plaques, covered in a silvery scale, often symmetrically placed and commonly plaques on the elbows and knees.
The diagnosis is usually clear but conditions such as Bowen's disease, drug eruptions, Lichen Planus, Lichen Simplex, Discoid Lupus Erythematosus, or pityriasis rosea, may present with similar plaques. Treatment depends on severity and extent of psoriasis but may involve topical corticosteroids, Vitamin D analogues, Dithranol and tar, phototherapy, or with specialist advice, oral treatment with methotrexate, acetretin or ciclosporin.