A 38-year-old man presents with erythematous, well-demarcated plaques with silvery scales on his elbows, knees, and scalp for the past 6 months. Dermoscopy shows regular psoriasiform acanthosis. What is the most common clinical type of psoriasis in this patient?

Explanation

## Diagnosis: Plaque Psoriasis **Key Point:** Plaque psoriasis (chronic plaque psoriasis) accounts for approximately 85–90% of all psoriasis cases and is the most common clinical presentation. ### Clinical Features of Plaque Psoriasis - Well-demarcated, erythematous plaques with silvery-white scales - Predilection for extensor surfaces: elbows, knees, shins, sacrum - Scalp involvement is very common - Auspitz sign (pinpoint bleeding when scale is removed) and Koebner phenomenon (lesions at trauma sites) are characteristic - Chronic course with periods of remission and exacerbation ### Comparison with Other Types | Feature | Plaque Psoriasis | Guttate Psoriasis | Inverse Psoriasis | Erythrodermic Psoriasis | |---------|------------------|-------------------|-------------------|------------------------| | **Frequency** | 85–90% | 7–10% | 3–7% | <3% | | **Morphology** | Large plaques (>1 cm) | Raindrop-like papules (<1 cm) | Smooth, shiny plaques | Confluent erythema | | **Sites** | Extensor surfaces | Trunk, proximal limbs | Intertriginous areas | Generalized (>80% BSA) | | **Trigger** | Chronic, variable | Often post-streptococcal | Friction, sweat | Systemic triggers, drug withdrawal | | **Prognosis** | Chronic, stable | Often self-limited | Chronic | Acute, severe | **High-Yield:** The classic presentation of plaque psoriasis on extensor surfaces (elbows, knees) with silvery scales is the "textbook" image every NEET PG candidate must recognize. **Clinical Pearl:** Scalp involvement in plaque psoriasis is present in up to 50% of patients and may be the sole manifestation in some cases, often misdiagnosed as seborrheic dermatitis. **Mnemonic: ELKS** — Elbows, Knees, Scalp (the classic extensor sites for plaque psoriasis).