Which of the following is the hallmark histopathological finding in psoriasis?

Explanation

## Histopathology of Psoriasis **Key Point:** The classic triad of psoriatic histology is: 1. **Parakeratosis** — retention of nuclei in the stratum corneum (abnormal keratinization) 2. **Regular acanthosis** — uniform thickening of the epidermis with elongation of rete ridges 3. **Dilated capillaries in dermal papillae** — tortuous, dilated vessels in the papillary dermis ### Distinguishing Features | Feature | Psoriasis | Eczema | Lichen Planus | |---------|-----------|--------|---------------| | Parakeratosis | Present | Absent | Absent | | Acanthosis | Regular, uniform | Irregular | Lichenoid | | Granular layer | Absent/thin | Present | Preserved | | Capillaries | Dilated, tortuous | Normal | Normal | | Infiltrate | Superficial dermis | Superficial dermis | Dense band-like | **High-Yield:** The combination of **parakeratosis + regular acanthosis + absent granular layer** is virtually pathognomonic for psoriasis. **Clinical Pearl:** Dilated capillaries in the dermal papillae are responsible for the pinpoint bleeding (Auspitz sign) when scale is removed from a psoriatic plaque. ### Why Other Options Are Wrong - Option 1 (correct): Contains all three hallmark features - Option 2: Describes eczema/dermatitis (spongiosis, preserved granular layer) - Option 3: Describes lichen planus (lichenoid infiltrate, basal degeneration) - Option 4: Basket-weave pattern is normal stratum corneum; psoriasis shows parakeratosis instead