Which of the following is the most characteristic histopathological finding in psoriasis?

Explanation

## Histopathology of Psoriasis **Key Point:** The **most characteristic** (pathognomonic) histopathological finding in psoriasis is **acanthosis with regular elongation of rete ridges combined with thinning of the suprapapillary epidermis** — this architectural pattern is unique to psoriasis among inflammatory dermatoses. ### Characteristic Histological Features of Psoriasis | Feature | Finding | |---------|---------| | Stratum corneum | Hyperkeratosis with **parakeratosis** | | Stratum granulosum | **Absent or markedly diminished** | | Rete ridges | **Regular acanthosis** — elongated, club-shaped ("test tube" pattern) | | Suprapapillary epidermis | **Thinned** (2–3 cell layers) | | Dermal papillae | Edematous with **dilated, tortuous capillaries** | | Neutrophilic collections | **Munro microabscesses** (in stratum corneum) | ### Why Option A is the Most Characteristic Finding The combination of **regular acanthosis with elongated rete ridges + thinning of the suprapapillary epidermis** is the defining architectural hallmark of psoriasis (Andrews' Diseases of the Skin; Lever's Histopathology of the Skin). This pattern distinguishes psoriasis from other papulosquamous disorders. The thinned suprapapillary plate over dilated papillary capillaries directly explains the **Auspitz sign** (pinpoint bleeding on scale removal). ### Why the Other Options Are Incorrect - **Option B (Spongiosis with intraepidermal microabscesses):** Spongiosis is characteristic of **eczematous/spongiotic dermatitis**, NOT psoriasis. Psoriasis shows minimal spongiosis. - **Option C (Hyperkeratosis with parakeratosis and dilated capillaries):** These are real psoriasis features but are **not the most discriminating** — parakeratosis occurs in many conditions (seborrheic dermatitis, pityriasis rosea). The architectural change in Option A is more specific. - **Option D (Lichenoid infiltrate with basal cell degeneration):** This is the hallmark of **lichen planus**, not psoriasis. **High-Yield Mnemonic — APART:** **A**canthosis (regular), **P**arakeratosis, **A**bsent granular layer, **R**ete ridges elongated, **T**hinned suprapapillary plate. **Clinical Pearl:** The accelerated epidermal turnover (7–10 days vs. 28 days normal) drives the regular acanthosis and parakeratosis, while increased vascularity produces the dilated papillary capillaries — all reflected in the pathognomonic architectural pattern of Option A. *Reference: Lever's Histopathology of the Skin, 11th ed.; Andrews' Diseases of the Skin, 13th ed.*