Pustular psoriasis

There are two main variants of this type of psoriasis, palmar plantar pustulosis (PPP) and generalised pustular psoriasis (GPP). Some clinicians consider PPP to be a totally different entity from other types of psoriasis. About 70–80% of patients who have PPP will not have any other psoriatic lesions elsewhere on the body (Figure 8.6). It is also worth noting that significantly more women than men suffer with PPP and that its onset is generally later in life. It is very strongly associated with smoking. Its appearance is of pustules against a background of erythema and scaling. Pustules at different stages will be present at any one time. Initially they are yellowish in colour (although the contents are sterile) and when the pustule breaks, the skin forms brownish macules.

GPP should be considered a dermatological emergency where the patient is generally febrile and unwell. Whilst GPP affects both sexes equally, like PPP it tends to occur later in life (around 50) and can evolve from a preexisting psoriasis or occur without any psoriasis history. It is relatively rare with only around 2% of the psoriasis population ever experiencing GPP. A strong trigger factor for the development of GPP appears to be commencement on, or withdrawal from, systemic steroids; however, infection or other drug reactions may also cause GPP. GPP can affect any part of the body but seems to have a predilection for flexural areas. There are hundreds of superficial pustules on widespread, irregular patches of bright red skin. These patches tend to have serpiginous or wavy borders which move as the pustules coalesce and then desquamate.