21.4 Aesthetic & Corrective Dermatology, Photodynamic Therapy & Dermatological Radiotherapy

21.4 Aesthetic & Corrective Dermatology, Photodynamic Therapy & Dermatological Radiotherapy

Lasers and electrosurgery are covered in the cryosurgery, electrosurgery, and laser section. This section focuses on injectables, peels, other aesthetic devices, photodynamic therapy (PDT), and radiotherapy.

Patient Selection and Regulation

• Assess the patient's expectations and screen for body dysmorphic disorder, in which cosmetic procedures should generally be avoided (see the psychodermatology section).
• Record medical history, drugs (anticoagulants, isotretinoin), previous procedures and fillers, and keep standard photographs. Obtain written informed consent that covers alternatives and risks.
• In the EU, products without a medical purpose, such as dermal fillers and many energy-based aesthetic devices, are regulated under the Medical Device Regulation (Annex XVI). National rules differ on who may inject.

Botulinum Toxin Type A

• Mechanism: the light chain cleaves SNAP-25, a SNARE protein, and blocks acetylcholine release at the neuromuscular junction and at sweat glands.
• Time course: onset about 2–3 days, peak about 2 weeks, duration about 3–4 months in muscle (longer for sweating).
• Products: onabotulinumtoxinA, abobotulinumtoxinA, and incobotulinumtoxinA (free of complexing proteins). Units are not interchangeable between products.
• Common indications: glabellar lines (corrugator and procerus), lateral canthal lines (orbicularis oculi), forehead lines (frontalis), and primary hyperhidrosis.

Contraindications: pregnancy and breastfeeding, neuromuscular disorders (myasthenia gravis, Lambert-Eaton syndrome), infection at the site, and caution with aminoglycosides. Repeated high doses can induce neutralising antibodies.

Dermal Fillers

Complications

• Early: swelling, bruising, lumps, infection, hypersensitivity, and the Tyndall effect (blue-grey discolouration from HA placed too superficially, treated with hyaluronidase).
• Vascular occlusion (emergency): filler injected into or compressing an artery causes immediate pain and blanching, then a reticulate livedo pattern, dusky discolouration, and necrosis. Stop injecting, give high-dose hyaluronidase (repeated until reperfusion) for HA fillers, apply warm compresses and massage, and consider aspirin.
• Blindness: retrograde embolism into the ophthalmic artery causes sudden visual loss, pain, and ptosis. It is most linked to the glabella, nose, nasolabial fold, and forehead. It needs emergency ophthalmology review. The outcome is often poor, so prevention (anatomy, aspiration, slow low-pressure injection, cannulas in danger zones) is vital.
• Late: inflammatory or biofilm-related nodules, delayed-onset nodules after infections or vaccination, and foreign-body granulomas.

Chemical Peels

Complications: post-inflammatory hyperpigmentation (especially in darker skin types), infection (including herpes simplex), scarring, and lines of demarcation. Avoid medium and deep peels during or shortly after isotretinoin, with active herpes simplex, and in pregnancy.

Other Aesthetic Devices and Procedures

• Intense pulsed light (IPL): broadband light (about 500–1,200 nm) with filters for vascular lesions, lentigines, and hair removal.
• Laser hair removal: alexandrite (755 nm), diode (about 810 nm), and Nd:YAG (1,064 nm) for darker skin types. Paradoxical hypertrichosis is a recognised side effect.
• Tattoo removal: Q-switched and picosecond lasers. White, flesh-coloured, and some red inks containing iron or titanium oxide can darken paradoxically. Red tattoo ink is a common cause of allergic reactions.
• Radiofrequency, microneedling, and high-intensity focused ultrasound: skin tightening and scar improvement.
• Cryolipolysis: non-invasive fat reduction; paradoxical adipose hyperplasia is a rare complication.
• Sclerotherapy of leg telangiectasia and reticular veins: see the phlebology section.

Photodynamic Therapy (PDT)

• Principle: a topical precursor, 5-aminolevulinic acid (ALA) or methyl aminolevulinate (MAL), is converted in abnormal cells to protoporphyrin IX. Light activates it to form reactive oxygen species that destroy the cells.
• Light sources: red light (about 630–635 nm) for conventional PDT, blue light, or daylight.
• Indications: actinic keratoses and field cancerisation, Bowen disease, and superficial (and thin nodular) basal cell carcinoma. It is not used for invasive squamous cell carcinoma or melanoma.
• Daylight PDT: European consensus supports it for grade I–II actinic keratoses on the face and scalp. It is as effective as conventional PDT and much less painful.
• Side effects: pain during illumination (conventional PDT), erythema, oedema, crusting, and temporary pigment change. Cosmetic results are usually very good.

Dermatological Radiotherapy

• Types: superficial X-rays (including very low-energy Grenz rays), electron beam, and brachytherapy.
• Indications:
  • Basal cell and squamous cell carcinoma in older patients, or where surgery would be difficult (eyelid, nose, lip, ear).
  • Adjuvant radiotherapy for high-risk cSCC (for example positive margins or major nerve involvement) and for Merkel cell carcinoma.
  • Lentigo maligna in selected patients unsuitable for surgery.
  • Cutaneous lymphomas (localised radiotherapy, total skin electron beam therapy for mycosis fungoides) and Kaposi sarcoma.
  • Keloids, as adjuvant treatment soon after excision.
• Cautions and contraindications: Gorlin syndrome and xeroderma pigmentosum (radiation induces new tumours), younger patients (late skin changes and second cancers appear over decades), previously irradiated sites, poorly healing areas such as the lower leg, and some connective tissue diseases (systemic sclerosis).
• Late effects: atrophy, telangiectasia, pigment change, fibrosis, alopecia, and radiation-induced cancers (see the physical injury section).