Erythrodermic psoriasis presents as an intense, bright-red, inflmmatory dermatitisinvolving at least 75% of the body surface area (Figure 17.1) [10]. It is rare, with an estimated prevalence of 1%–2.25% among psoriasis patients, and can occur de novo or in patients with preexisting psoriasis [11]. Patients may appear ill—with fever, chills, and malaise [11]. The course of erythrodermic psoriasis varies from acute and rapidly progressive to prolonged and chronic, which may follow a relapsing–remitting pattern.
Psoriasis is the most common cause of erythroderma and represents about 25% of cases.
Other causes of erythroderma include cutaneous lymphoma, pityriasis rubra pilaris, severe
eczema, and drug eruptions [12–14]. Ths, biopsy may be useful in distinguishing erythrodermic psoriasis from these other causes of erythroderma.
Pustular psoriasis has been historically classifid into two forms: localized and generalized.
Generalized pustular psoriasis can be further divided based on the acuity of presentation
and natural history of disease. Annular pustular psoriasis usually follows a chronic, more
benign course. In contrast, the von Zumbusch type is oftn a more severe presentation, characterized by the rapid onset of widespread sterile pustules on a background of erythema
(Figure 17.2) [15]. Like erythrodermic psoriasis, preexisting psoriasis vulgaris may or may
not be present [16]. Initially, pustules may be located at the periphery of psoriatic plaques,
where inflmmation is the most active. However, once the disease becomes generalized, it
can develop on any involved skin [17]. Conflence of these pustules may form irregular
“lakes of pus” over part or all of the body. Th patient may appear toxic, with fever, chills,
pain, and intense pruritus [18]. Other possible fidings include a geographic or fisured
tongue, scaly lips with superfiial ulcerations, and ocular involvement (e.g., conjunctivitis,
uveitis, or iritis).
