PUVA Therapy

PUVA Therapy - The Dynamic Duo

• Combines Psoralen (e.g., 8-methoxypsoralen) with UVA light (320-400 nm).
• Mechanism: Psoralen intercalates into DNA. UVA photoactivation leads to covalent bonds.
• Forms DNA monoadducts and interstrand crosslinks (ISCLs).
• Result: Inhibits keratinocyte hyperproliferation; induces T-cell apoptosis.
• Key Indications: Severe psoriasis, vitiligo, mycosis fungoides, chronic GVHD.
• 📌 Psoralens Under Violet Activate.

⭐ PUVA primarily forms DNA monoadducts and interstrand crosslinks, inhibiting keratinocyte proliferation.

PUVA Therapy - The Active Agents

• Psoralens (P): Photosensitizing agents.
  • Types: 8-methoxypsoralen (8-MOP), 5-methoxypsoralen (5-MOP), Trimethylpsoralen (TMP).
  • Mechanism: Intercalate with DNA; upon UVA activation, form cyclobutane adducts with pyrimidine bases, inhibiting DNA replication.

  ⭐ Oral 8-methoxypsoralen (8-MOP) is the most widely used psoralen, typically administered 1.5-2 hours before UVA exposure.

• UVA Light (UVA): Long-wave ultraviolet radiation.
  • Wavelength: 320-400 nm (peak action spectrum 320-340 nm).

PUVA Therapy - Disease Targets

• Psoriasis
  • Moderate to severe chronic plaque psoriasis
  • Palmoplantar psoriasis
  • Guttate psoriasis (second-line)
  • Pustular psoriasis (palmoplantar, generalized)
  • Erythrodermic psoriasis
• Vitiligo (generalized)
• Mycosis Fungoides (Cutaneous T-cell Lymphoma - CTCL) - patch/plaque stage
• Atopic Dermatitis (severe, recalcitrant)
• Lichen Planus (generalized, hypertrophic)
• Polymorphous Light Eruption (prophylaxis)
• Urticaria Pigmentosa (symptomatic relief)
• Alopecia Areata (extensive)

⭐ PUVA is a first-line treatment for moderate to severe psoriasis, particularly chronic plaque type and palmoplantar psoriasis.

PUVA Therapy - The Treatment Plan

• Psoralen: Oral 8-methoxypsoralen (8-MOP) 0.6-0.8 mg/kg, 1.5-2 hours before UVA.
• UVA Exposure:
  • Initial dose: Based on Minimal Erythema Dose (MED) or skin phototype (SPT).
  • Frequency: 2-3 times/week (non-consecutive days).
  • Increments: ↑ UVA by 0.5-1.0 J/cm² per session, guided by erythema.
• Maintenance: Taper frequency once clear (e.g., weekly).
• Monitoring: Track cumulative UVA dose; consider risks with >200-250 sessions or >1000-1500 J/cm².

⭐ Patients must wear UVA-blocking sunglasses for 24 hours after psoralen ingestion, even indoors, to prevent cataract formation.

PUVA Therapy - Safety First

• Acute Side Effects:
  • Phototoxicity: Erythema, edema, blistering (dose-dependent)
  • GI upset: Nausea, vomiting (common with oral psoralen)
  • Pruritus, xerosis
  • Headache, dizziness
• Long-term Risks:
  • Premature skin aging (photoaging), PUVA lentigines
  • Cataractogenesis (strict eye protection essential for 24h post-psoralen)

  ⭐ The most significant long-term risk of PUVA therapy is an increased dose-dependent risk of squamous cell carcinoma (SCC).

• Key Contraindications:
  • Pregnancy, lactation
  • Severe hepatic or renal impairment
  • Photosensitivity disorders (e.g., SLE, XP, porphyria)
  • History of melanoma or multiple NMSCs

High‑Yield Points - ⚡ Biggest Takeaways

• PUVA: Psoralen + UVA (320-400 nm); forms DNA adducts, inhibiting cell proliferation.
• Key uses: Severe psoriasis, vitiligo, CTCL, atopic dermatitis.
• Dose: Based on MED or skin phototype.
• Acute effects: Phototoxicity (erythema, blisters), nausea, pruritus.
• Long-term: Skin aging, cataracts, ↑ SCC risk (especially skin types I/II).
• Mandatory eye protection (UVA-blocking) for 24h post-psoralen.
• Avoid in pregnancy, melanoma history, severe photosensitivity disorders_._