Pustular Psoriasis: The Dawn of a New Era

Abstract

Pustular psoriasis is a clinically heterogeneous entity of different, orphan disease subtypes, among which the most clearly defined are generalized pustular psoriasis, palmoplantar psoriasis, and acrodermatitis continua of Hallopeau. Although phenotypically and genetically distinct from psoriasis vulgaris, these subtypes may be associated with plaque psoriasis lesions, establishing the rationale for their inclusion in the psoriasis spectrum. Unlike psoriasis, however, their genetic background is thought to be mainly monogenic, as shown by the recent identification of mutations in 3 different genes of the skin innate immune system; IL36RN, CARD14 and AP1S3. These major advances in the understanding of the disease pathogenesis have led to the design and ongoing development of tailored therapeutic approaches, which are highly necessary given the refractory nature of pustular psoriasis in response to most available antipsoriatic drugs.

Keywords: generalized pustular psoriasis; interleukin-36; palmoplantar pustulosis; pustular psoriasis; pustulosis.

Fig. 1

Skin lesions in patients with generalized pustular psoriasis. (A) A diffuse erythema is covered with confluent pustules, leading to formation of pustular lake, with superficial scaling at a later stage, in a patient free of IL36RN or CARD14 mutation. (B) Disseminated, separated pustules on an erythematous basis of the forearm of an adult patient with identified deficiency of IL36 receptor antagonist.

Fig. 2

Typical lesions of palmoplantar pustular psoriasis in 3 different patients free of any mutation in IL36RN, CARD14 and AP1S3 genes. (A) Pustular lesions involving palmar areas of hands, with some degree of acropustular damage, reflecting the possible association between palmoplantar pustular psoriasis and acrodermatitis continua of Hallopeau (ACH). (B) Disseminated pustules of the soles leave dark-brown macular lesions, coexisting with fresh evolutive pustules and erythemato-squamous lesions. (C) Typical lesions of ACH involving the toes, leading to destruction of the nail apparatus.