Most cases of established psoriasis are easy to diagnose with typical salmon red plaques and silvery white scale in a symmetrical distribution on extensor surfaces. The problem arises with early cases or atypical sites and atypical presentations.
Tip 1 – Psoriasis can start at any age and although it has peak incidence in the 2nd and 6th decades of life it should be considered in the differential diagnosis at any age. Some patterns of psoriasis such as palmar plantar pustular psoriasis usually affect middle aged women (particularly who smoke). In elderly patients over the age of 70 the onset of psoriasis is often in a seborrhoeic distribution.
Tip 2 – Always check the fingernails and ears as these can give confirmatory evidence of psoriasis in patients where the disease is at an early stage (before the appearance of the classical plaques). In a patient with a new erythematous symmetrical rash, the presence of a couple of nail pits/early onycholysis or the presence of scaling behind the ear may be enough to confirm a new diagnosis of psoriasis.
Nail disease confirms diagnosis
Tip 3 – Flexural psoriasis (eg sub-mammary, natal cleft) does not usually have the typical plaques of ordinary psoriasis. Usually, flexural psoriasis causes a shiny erythematous patch with little overlying scale and can resemble candidal intertrigo. It lacks the satellite pustules of candidiasis and is usually not itchy and not as sore as candidiasis.
Tip 4 – Seborrhoeic dermatitis and psoriasis often overlap. In patients with facial or scalp involvement with psoriasis the distribution is often in a seborrhoeic pattern as a result of the Koebner phenomenon where the inflammation of seborrhoeic dermatitis induces psoriasis. This overlap should be suspected in any ‘seborrhoeic dermatitis’ which is difficult to treat.
Tip 5 – Beware making a diagnosis of psoriasis when the patient has only a solitary scaly erythematous patch. Psoriasis is almost always symmetrical and a solitary patch, particularly on the leg, could represent Bowen’s disease (squamous cell carcinoma in situ) or basal cell carcinoma (picture below) or even tinea corporis
Single plaque could be basal cell carcinoma
Mild psoriasis is fairly easy to treat in most patients and usually needs a combination of emollients and topical vitamin D analogues and/or topical steroid. Very severe cases will often need phototherapy or systemic agents and are best referred to a secondary care dermatology department for this. There is, however, a group of patients with mild-moderately severe psoriasis who need some additional help to keep their psoriasis managed without referral to secondary care.
Tip 6 – Manage the expectations that your patient has from their disease and their treatment. Most patients with existing psoriasis realise that it is a chronic condition particularly if they have a family member who is affected. The new patient need to know that psoriasis can be controlled, but not cured and that the aim of treatment is to control their psoriasis sufficiently to lead a near normal life. This means achieving a level of control which is not perfect, but which is ‘good enough’.
Tip 7 – Look at lifestyle factors which have an adverse impact on psoriasis. The most important of these are stress and alcohol intake. It may be possible for a patient to go from severe disease which requires systemic agents to mild disease which can be controlled with topical treatment simply by cutting out regular alcohol use. It may also help patients to realise that stressful events can trigger a flare of psoriasis and that a reduction workplace stress can improve their psoriasis or make it easier to treat.
Tip 8 – Make the treatment as easy as possible for the patient and they are much more likely to use it. Patients prefer once daily treatment which is quick to apply and cosmetically acceptable. This may mean using combination treatments such as vitamin D analogue/steroid combinations, but also means using formulations which suit the patient eg an emollient cream rather than an ointment. Some combination products such as steroid/antifungal/antibiotic combinations are particularly useful if there is overlap with seborrhoeic dermatitis. There are some preparations which are quite unfriendly to patients, but which are still very useful (eg coal tar products – patients dislike the smell) and limiting these to once weekly use will improve usage.
Tip 9 – Coal tar in the form of a bath emollient, shampoo, scalp ointment or other preparations is still a very useful treatment in psoriasis where itch is a significant symptom. Whilst classical psoriasis is not particularly itchy, some patients do have troublesome itch and coal tar has stood the test of time in terms of effectiveness and safety.
Tip 10 – Natural sunlight is a very important way of improving psoriasis. The vast majority of patients improve in the summer and many patients only clear their disease by going on sun holidays. The potential for natural sunlight to cause skin cancer, however needs to be balanced with the beneficial effects. The use of tanning sunbeds is more risky (and not recommended) as the dosage of ultraviolet radiation is impossible to monitor and, unlike natural sunlight, there is no heat to give patients an idea of how much radiation they are receiving.
Unfortunately, some patients are so self conscious of their psoriasis that they are reluctant to expose their skin to sunlight and miss its benefits; these patients (and any not responding to topical therapy) may be suitable for referral for phototherapy in secondary care.