Guttate Psoriasis

Definition & Etiology - Raindrop Eruption

• Definition: An acute, eruptive variant of psoriasis. Presents as multiple, small (0.5-1.5 cm diameter), discrete, erythematous papules and plaques with fine scale. Often described as having a "raindrop" or "dewdrop" appearance. Predominantly affects the trunk and proximal extremities.
• Etiology:
  • Primary Trigger:

    ⭐ Strong association with preceding Group A beta-hemolytic streptococcal (GABHS) infection (e.g., pharyngitis, tonsillitis), typically 2-3 weeks prior.

  • Pathomechanism: Likely T-cell mediated immune response; molecular mimicry between streptococcal M proteins and skin keratins is implicated.
  • Genetic Predisposition: Strong association with HLA-Cw6.
  • Other Factors: Upper respiratory tract viral infections, stress, and rarely, medications can also trigger episodes.

erythematous 'raindrop' papules with fine scale on trunk)​

Clinical Presentation - Spotting the Shower

• Trigger: Often 1-3 weeks post-streptococcal infection (e.g., pharyngitis).
• Lesions:
  • Small, discrete, erythematous papules (0.5-1.5 cm).
  • Classic "tear-drop" or "rain-drop" appearance (📌 Gutta = Drop).
  • Fine, silvery scales; often thinner than plaque psoriasis.
  • Auspitz sign may be positive.
• Distribution:
  • Widespread, primarily on trunk & proximal extremities.
  • Face, scalp, ears less common; palms/soles usually spared.
• Symptoms: Pruritus common, variable intensity.
• Koebner Phenomenon: Can occur (new lesions at trauma sites).
• Nails/Joints: Typically unaffected.

⭐ Characterized by sudden onset of multiple, small (0.5-1.5 cm), erythematous, scaly papules and plaques resembling "raindrops" (gutta = drop in Latin), primarily on trunk and proximal extremities.

Diagnosis & DDx - Pinpointing Psoriasis

• Clinical Diagnosis: Primarily based on characteristic history (sudden onset, often post-streptococcal infection) and morphology (small, erythematous, scaly papules - "dewdrop" or "raindrop" appearance).
• Investigations:
  • Throat swab: For Group A β-hemolytic Streptococcus (GAS).
  • ASO titer: ↑ Anti-Streptolysin O titer suggests recent streptococcal infection.
  • Biopsy (rarely needed): Shows parakeratosis, Munro's microabscesses, acanthosis, suprapapillary thinning.

⭐ Elevated Anti-Streptolysin O (ASO) titer or positive throat culture for Streptococcus pyogenes supports the diagnosis.

• Differential Diagnosis (DDx):
  • Pityriasis rosea: Herald patch, "Christmas tree" pattern, collarette of scale.
  • Lichen planus: Purple, polygonal, pruritic papules/plaques (4 P's).
  • Secondary syphilis: Papulosquamous lesions, often on palms/soles, serology positive.
  • Nummular eczema: Coin-shaped, intensely pruritic plaques.
  • Tinea corporis: Annular lesions with central clearing, KOH positive for fungi.
  • Drug eruptions: Variable morphology, history of new medication. 📌 Remember DRUGS (Drug Reaction with Eosinophilia and Systemic Symptoms).

Management & Prognosis - Calming the Cascade

• Goals: ↓inflammation, ↓scaling, induce remission.
• Initial/Mild Cases:
  • Emollients: Hydration is key.
  • Topical corticosteroids: Mild to moderate potency (e.g., fluticasone, triamcinolone) for 2-4 weeks.
  • Vitamin D analogues: (e.g., calcipotriol) alone or with steroids.
• Widespread/Severe Cases:
  • Phototherapy:

    ⭐ Narrow-band UVB (NB-UVB) is first-line for widespread guttate psoriasis; often leads to rapid resolution.

    • Broad-band UVB (BB-UVB) also effective.
  • Systemic therapy (rarely needed, if persistent/severe):
    • Methotrexate, cyclosporine, acitretin.
    • Biologics (e.g., TNF-α inhibitors) if refractory.
• Prognosis:
  • Often self-limiting; resolves in weeks to months (typically 3-4 months).
  • ~1/3 develop chronic plaque psoriasis.
  • Recurrences possible, especially with new streptococcal infections.

High-Yield Points - ⚡ Biggest Takeaways

• Acute onset of small, "drop-like" (guttate) papules and plaques.
• Commonly triggered by Group A β-hemolytic streptococcal infection, especially pharyngitis, 2-3 weeks prior.
• Predominantly affects the trunk and proximal extremities.
• More frequent in children and young adults.
• Elevated ASO titres are often found.
• Auspitz sign and Koebner phenomenon may be present.
• Often self-limiting, but can precede or coexist with chronic plaque psoriasis.