Pustular Psoriasis

Overview & Classification - Pustule Parade

• Characterized by widespread or localized sterile pustules on erythematous base; distinct from plaque psoriasis.
• Can be life-threatening (e.g., GPP).

Classification:

• Generalized Pustular Psoriasis (GPP)
  • Von Zumbusch variant (acute, febrile)
  • Impetigo herpetiformis (psoriasis of pregnancy)
  • Annular/circinate variant
  • Infantile/juvenile GPP
• Localized Pustular Psoriasis
  • Palmoplantar Pustulosis (PPP)
  • Acrodermatitis Continua of Hallopeau (ACH)

⭐ Generalized Pustular Psoriasis (GPP) can be triggered by rapid withdrawal of systemic corticosteroids or potent topical steroids, infections, or certain medications (e.g., lithium, antimalarials).

Generalized Pustular Psoriasis (GPP) - Fiery Outbreak

• Acute, severe, potentially life-threatening; widespread sterile pustules coalescing into "lakes of pus" on erythematous skin.
• Systemic: high fever, chills, arthralgia, ↑leukocytosis.
• Triggers:
  • Corticosteroid withdrawal (most common).
  • Infections, hypocalcemia, pregnancy (impetigo herpetiformis), drugs (lithium, antimalarials).
• Skin: fiery red, tender, burning. Nail changes common.
• Management: Hospitalization. First-line: Acitretin. Alternatives: Cyclosporine, Methotrexate, Biologics (e.g., infliximab). Avoid systemic steroids (rebound risk).

⭐ Impetigo herpetiformis is GPP of pregnancy, often linked to hypocalcemia and typically occurs in the third trimester.

Localized Pustular Psoriasis - Sticky Spots

• Chronic, relapsing sterile pustules on specific sites.
• Palmoplantar Pustulosis (PPP):
  • Palms & soles; often symmetrical.
  • Yellow pustules, erythema, scaling, fissures.
  • Strongly associated with smoking (up to 95%).
  • Nail involvement common.
• Acrodermatitis Continua of Hallopeau (ACH):
  • Rare; affects distal digits (fingers/toes), periungual.
  • Painful pustules, nail dystrophy, onycholysis, anonychia.
  • May lead to osteolysis.

⭐ ACH can cause irreversible bone resorption (osteolysis) of the distal phalanx an_d nail loss (anonychia).

Pathogenesis & Histology - Microscopic Mayhem

• Pathogenesis:
  • Genetic: IL36RN mutations (DITRA - Deficiency of IL-36 Receptor Antagonist).
  • Triggers: Infections, stress, rapid steroid withdrawal, hypocalcemia, pregnancy.
  • Key Cytokines: ↑ IL-36, IL-1, IL-17, IL-23, TNF-α → massive neutrophil chemotaxis.
• Histology:
  • Kogoj's spongiform pustules: Hallmark; intraepidermal neutrophil collections.
  • Munro's microabscesses: Neutrophils in stratum corneum.
  • Epidermis: Acanthosis, parakeratosis.
  • Dermis: Papillary edema, perivascular infiltrate (neutrophils, lymphocytes).

⭐ IL36RN gene mutations are strongly linked to Generalized Pustular Psoriasis (GPP), resulting in DITRA syndrome and uncontrolled IL-36 inflammation.

Diagnosis & Management - Calming the Storm

• Diagnosis:
  • Clinical: Sudden widespread sterile pustules, erythema, fever, pain.
  • Biopsy: Kogoj's spongiform pustules (key).
  • Labs: Leukocytosis (neutrophilia), ↑ESR/CRP, hypocalcemia.
• Management:
  • Goals: Rapid pustule clearance, systemic symptom control.
  • Supportive: Hydration, electrolyte correction (esp. Ca), emollients.
  • GPP (Generalized Pustular Psoriasis): Hospitalize.
    • Systemic 1st line: Acitretin (0.5-1 mg/kg/d), Cyclosporine (2.5-5 mg/kg/d), Biologics (e.g., Infliximab, Spesolimab).
    • Alternatives: Methotrexate (slower), other biologics (IL-17, IL-23 inhibitors).
  • Localized (e.g., Palmoplantar Pustulosis - PPP): Potent topical steroids + Vit D analogs. Refractory: Acitretin.
  • ⚠️ Avoid abrupt systemic steroid withdrawal (risk of severe rebound).

⭐ Spesolimab, an IL-36 receptor antibody, is a targeted therapy for GPP flares.

High‑Yield Points - ⚡ Biggest Takeaways

• Generalized Pustular Psoriasis (GPP/von Zumbusch) is an acute, febrile, life-threatening systemic illness.
• Pustules in GPP are widespread, sterile, and develop rapidly on an erythematous base.
• Key GPP triggers: systemic steroid withdrawal, infections, hypocalcemia, pregnancy (impetigo herpetiformis).
• Palmoplantar Pustulosis (PPP) presents with chronic, sterile pustules on palms and soles; strong smoking association.
• Acrodermatitis Continua of Hallopeau (ACH) affects distal digits and nails, potentially leading to onychodystrophy and osteolysis.
• Histopathology classically shows Kogoj's spongiform pustules (subcorneal/intraepidermal neutrophilic aggregates).
• GPP management often requires systemic therapy: acitretin (first-line), cyclosporine, methotrexate, or biologics (e.g., IL-36R inhibitors).