A 42-year-old woman with a 12-year history of plaque psoriasis on her elbows and knees develops sudden onset of widespread small erythematous papules on her trunk and proximal arms following an upper respiratory tract infection. Which clinical feature best distinguishes this acute eruption (guttate psoriasis) from her chronic plaque psoriasis?

Explanation

## Acute Guttate vs. Chronic Plaque Psoriasis: Clinical Distinction **Key Point:** The defining feature of guttate psoriasis is **acute onset of small papules (drop-like, <1 cm) following a systemic trigger** (typically Group A Streptococcal pharyngitis or other URTI), in contrast to the insidious, chronic course of plaque psoriasis. ### Clinical Presentation Comparison | Aspect | Plaque Psoriasis | Guttate Psoriasis | | --- | --- | --- | | **Onset** | Insidious, gradual | Acute (days to weeks) | | **Trigger** | Koebner trauma, stress | Streptococcal URTI (classic) | | **Morphology** | Large plaques (>1 cm) | Small papules (<1 cm, "tear-drop") | | **Distribution** | Extensor surfaces, scalp | Trunk, proximal limbs | | **Speed of spread** | Slow over months/years | Rapid over days/weeks | | **Associated symptoms** | Usually asymptomatic | May have systemic symptoms (fever, malaise) | | **Natural history** | Persistent, relapsing | May self-limit or evolve to plaque type | **High-Yield:** A patient with **pre-existing plaque psoriasis who develops sudden widespread small papules after a streptococcal infection** is experiencing a guttate flare, not a new disease. The **acute temporal relationship to infection + small lesion size** is the best discriminator. **Mnemonic:** **GUTTATE = Guttate (drop-like) + Urgent (acute) + Throat infection (strep) + Tiny lesions (<1 cm) + Acute spread + Trunk distribution + Eruptive course** **Clinical Pearl:** Guttate psoriasis can occur de novo or as an acute exacerbation in patients with chronic plaque psoriasis (as in this case). Screening for Group A Streptococcal infection (throat culture, ASO titre) is warranted. Some patients benefit from antistreptococcal therapy (penicillin V) to prevent recurrence. ### Why Other Features Do NOT Distinguish - **Nail changes (pitting, onycholysis):** Occur in both plaque and guttate psoriasis; not discriminatory. - **Auspitz sign:** Present in both types; reflects the shared histopathology (parakeratosis). - **Scalp/postauricular involvement:** Plaque psoriasis favors scalp; guttate typically spares scalp—but this is a trend, not absolute.