Hypergranulosis in Pustular Psoriasis
No, hypergranulosis does not occur in pustular psoriasis—in fact, pustular psoriasis characteristically shows absent or diminished granular layer, which is the opposite of hypergranulosis.
Histopathologic Features of Pustular Psoriasis
Pustular psoriasis is defined by large collections of neutrophils in the stratum corneum that are clinically visible as pustules 1. The key histopathologic features include:
- Neutrophilic infiltration: Widespread pustules on an erythematous background containing sterile neutrophil collections 2, 3, 4
- Absent or reduced granular layer: This is a characteristic finding that distinguishes pustular variants from other conditions
- Parakeratosis: Retention of nuclei in the stratum corneum
- Acanthosis: Epidermal thickening
Why This Matters Clinically
The absence of hypergranulosis (and often the complete absence of the granular layer) is actually a distinguishing feature that helps differentiate pustular psoriasis from other dermatologic conditions. Hypergranulosis is typically seen in conditions like lichen planus or chronic friction dermatoses, not in psoriasis variants.
Pustular Psoriasis Variants
Both generalized and localized forms share this histopathologic pattern 1:
- Generalized pustular psoriasis (von Zumbusch variant): Severe form with fever, toxicity, and widespread pustules 1
- Localized palmoplantar pustular psoriasis: Confined to palms and soles 1
- Acropustulosis of Hallopeau: Affects terminal phalanges with nail destruction 5
Pathophysiology Context
Recent evidence demonstrates that pustular psoriasis, particularly generalized pustular psoriasis (GPP), is driven by dysregulation of the innate immune system with disruption of the IL-36 inflammatory pathway 3, 4. This is fundamentally different from plaque psoriasis, which involves adaptive immunity and IL-17. The neutrophil-dominant inflammation and rapid keratinocyte turnover in pustular psoriasis does not allow for the formation of a thickened granular layer (hypergranulosis).
Clinical Pitfall
Do not confuse pustular psoriasis with other pustular dermatoses that may show different histologic patterns. The combination of neutrophilic pustules, absent granular layer, and clinical presentation distinguishes pustular psoriasis from conditions like subcorneal pustular dermatosis or acute generalized exanthematous pustulosis (AGEP), which have different histopathologic features 2, 6.