Psoriasis pustulosaL40.1-L40.3

According to current doctrine, the term "pustular psoriasis" refers to a group of severe, localized or generalized skin diseases characterized by acute or chronic eruptions of neutrophilic pustules. The individual clinical variants are associated with concomitant psoriasis vulgaris to varying degrees.

According to localization and clinical picture one distinguishes:

• Pustular psoriasis (generalized type - PPG):
  • Pustular psoriasis generalisata
    • PPG (familial type)
    • PPG with signs of psoriasis vulgaris
    • PPG without signs of psoriasis vulgaris
  • Impetigo herpetiformis (especially in pregnancy)
  • Erythema anulare centrifugum-like psoriasis (pustulosa)
  • Infantile or juvenile pustular psoriasis
  • Paradoxical PPG under biologics
• Pustular psoriasis (localized type -PPP):
  • Psoriasis pustulosa palmaris et plantaris (Königsbeck-Barber type).
  • Psoriasis pustulosa palmaris et plantaris ( pustular bacterid Andrews type)
  • Acrodermatitis continua suppurativa (Hallopeau)
  • Paradoxical PPP under biologics

Pustular psoriasis represents a different type of reaction to psoriasis vulgaris, which can occur with or without the precursor stage of psoriasis vulgaris. However, there are patients in whom both manifestations alternate. Psoriasis vulgaris can also suddenly acquire a pustular component (psoriasis cum pustulatione).

Infections: Trigger factors for generalized pustular psoriasis are bacterial and viral (Epstein-Barr virus infections) infections, medication (antihypertensives, terbinafine, chloroquine), pregnancy (see impetigo herpetiformis) or sudden withdrawal of systemic glucocorticoid therapy. Paradoxical pustular reactions under therapy with biologics are rare (P Weisenseel 2016).

Genetics: The rare cases of familial PPG are associated with mutations of the interleukin-36 receptor gene (IL-36RN gene), which encodes the receptor protein interleukin-36a. IL-36a is an antagonist of 3 proinflammatory interleukins of the IL-1 family (IL-36alpha, IL-36beta, IL-36gamma). Its dysfunction leads to a predominance of pro-inflammatory cytokines. Such mutations are also found in about 80% of sporadic cases without symptoms of psoriasis vulgaris.

Associations with CARD14 have also been demonstrated (Bachelez H 2020).

In contrast, IL-36RN gene mutations are only found in 10% of PPG when associated with psoriasis vulgaris.

Note: Mutations in the IL-36RN gene can also be detected in exfoliatio areata linguae.

Another mutation associated with pustular psoriasis generalisata affects the adaptor protein complex 1 gene/AP1S3 gene. This variant leads to destabilization and malfunction of the pattern recognition receptor TLR-3 (Toll-like receptor 3/Toll-like receptors are used to recognize so-called "pathogen associated molecular patterns" PAMPs).

In a larger study (Twelves S et al. 2019/n=863 patients), the association of psoriasis vulvgaris with the psoriasis pustulosa variants was examined. The incidence of psoriasis vulgaris was lowest in PPP at 15.8% compared to 54.4% in GPP and 46.2% in ACH. The mean age for GPP was 31.0 years, for PPP 43.7 years and for ACH 51.8 years). The proportion of female patients was higher in PPP (77.0 %) than in GPP (62.5 %). Although AP1S3 alleles were similarly common in all disease subtypes, IL36RN mutations were less common in patients with PPP than in those with GPP and ACH.

1. Twelves S et al. (2019) Clinical and genetic differences between pustular psoriasis subtypes. J Allergy Clin Immunol 143:1021-1026.
2. Navarini AA, et al. (2017) ERASPEN Network. European consensus statement on phenotypes of pustular psoriasis. J Eur Acad Dermatol Venereol. 31: 1792-1799
3. Weisenseel P et al (2016) Pustular psoriasis. Dermatologist 67: 445-453