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Dermatology
Photodermatologic Disorders
Built from Dermatology, 5th Edition
What’s inside
10 sections · 145 slides
Overview
- Scope of this topic
- What is a photodermatosis
- Classification of photodermatoses
- Immunologically mediated photodermatoses
- How common are these disorders
- Clues to the diagnosis of specific photodermatoses
Polymorphous Light Eruption
The most common photodermatosis worldwide, also known as polymorphic light eruption
- What is polymorphous light eruption
- Epidemiology
- Pathogenesis
- Why PMLE happens: the immune tolerance link
- From sun exposure to a visible eruption
- When and where PMLE appears
- Polymorphous light eruption of the face
- Appearance and variants
- PMLE of the upper extremity
- Papular variant in darker skin
- Pathology
- PMLE histopathology
- Distinguishing PMLE from other conditions
- Evaluation of photosensitivity with suggested laboratory investigations
- Treatment: photoprotection and hardening
- Other treatment options
- PMLE of the thigh
- PMLE papulovesicles on the upper back
Actinic Prurigo
A severe, itchy, sunlight-triggered eruption most common in Native American populations
- What is actinic prurigo
- Epidemiology
- Pathogenesis
- Clinical features on the face
- Involvement of covered skin
- Cheilitis and conjunctivitis
- Pathology and differential diagnosis
- Treatment
- Alternative systemic therapies
- Actinic prurigo of the hand and forearm
- Actinic prurigo of the ears and arms
Hydroa Vacciniforme
A very rare, scarring, childhood-onset photodermatosis linked to Epstein-Barr virus
- What is hydroa vacciniforme
- Epidemiology
- Pathogenesis: the Epstein-Barr virus link
- Classic hydroa vacciniforme: how it evolves
- Signs that point to the more severe LPD form
- Pathology
- How a classic HV lesion evolves
- Differential diagnosis and treatment
- Early hydroa vacciniforme
- Hydroa vacciniforme-like lymphoproliferative disorder in a child
Chronic Actinic Dermatitis
A persistent, eczema-like reaction to sun and sometimes visible light, mainly in older men
- What is chronic actinic dermatitis
- Epidemiology
- Pathogenesis
- A sharp cut-off at the collar
- Pigment change and sparing of protected folds
- Involvement of the hand and wrist
- Sites of sparing in chronic actinic dermatitis
- Course and a related variant
- Pathology and differential diagnosis
- Treatment
- Treatment for refractory disease
Solar Urticaria
A physical form of hives triggered by sun exposure, appearing within minutes
- What is solar urticaria
- Epidemiology
- Pathogenesis
- Clinical features
- Course and uncommon variants
- Pathology, diagnosis, and differential
- Treatment
Photosensitivity from Defective DNA Repair
Rare inherited disorders where damaged DNA cannot be properly repaired after sun exposure
- An overview of this group
- Inherited DNA-repair disorders: clinical features
- Inherited DNA-repair disorders: clinical features (continued)
- Inherited DNA-repair disorders: inheritance and photosensitivity
- Inherited DNA-repair disorders: molecular and laboratory findings
- Inherited DNA-repair disorders: molecular and laboratory findings (continued)
- Xeroderma pigmentosum: what it is
- Pathogenesis
- Skin and eye findings
- Neurologic and internal effects
- Treatment
- Cockayne syndrome
- Why Cockayne syndrome differs from XP
- Related disorders: COFS and UV-sensitive syndrome
- Trichothiodystrophy: what it is
- The PIBIDS features of trichothiodystrophy
- Brittle hair: the hallmark of TTD
- Treatment of trichothiodystrophy
- Bloom syndrome: chromosomal instability
- Clinical features and treatment of Bloom syndrome
- Rothmund-Thomson syndrome
- Clinical course and differential diagnosis
- Treatment of Rothmund-Thomson syndrome
Chemical- and Drug-Induced Photosensitivity
Two distinct reactions to light-sensitizing substances: phototoxicity and photoallergy
- Phototoxicity versus photoallergy
- History
- Common phototoxic and photoallergic agents
- Epidemiology and mechanisms
- Phototoxicity: typical presentation
- Other phototoxic patterns
- Special cases: dermatology drugs and plant contact
- Photoallergy and photopatch testing
- Photopatch test series and concentrations
- Interpreting photopatch test results
- Pathology, differential diagnosis, and treatment
- Hyperpigmentation from a drug-induced photo-eruption
- Phototoxic drug eruption due to doxycycline
- Endogenous photosensitivity: porphyrins
- Other endogenous causes
Photoaggravated Dermatoses
Existing skin diseases that are not caused by, but can be worsened by, sun exposure
- What it means for a disease to be photoaggravated
- Photoaggravated atopic dermatitis
- Photoaggravated dermatoses
- Diagnosis and treatment
- Grover disease: what it is
- Four histologic patterns of Grover disease
- Grover disease: four histologic patterns
- Differential diagnosis and treatment
- Grover disease on the back
Normal Effects of UVR and Visible Light
How ordinary skin reacts to sunlight, from a single sunburn to years of accumulated exposure
- Acute versus chronic effects
- Sunburn: the acute inflammatory reaction
- Sunburn: severity and treatment
- Pigment darkening and tanning
- Epidermal thickening and immune changes
- Vitamin D3 synthesis
- How UVB makes vitamin D3
- Other UVR-related skin changes
- Photoaging: cumulative sun damage
- Cutaneous signs of significant photodamage
- Cutaneous signs of significant photodamage (continued)
- Solar elastosis and cutis rhomboidalis nuchae
- Cutaneous signs of significant photoaging
- Solar lentigo versus ephelide (freckle)
- More signs of photoaging
- Erosive pustular dermatosis and other findings
- Photoaging in darker skin phototypes
- Photocarcinogenesis
- Further signs of significant photoaging
- Yellow discoloration from solar elastosis
- Favre-Racouchot syndrome of the temple
- Favre-Racouchot syndrome of the malar eminence
- Skin tear in severely photodamaged skin
- Keratoelastoidosis marginalis of the finger
- Key takeaways
- References
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- Dermatology, 5th Edition (2-Volume Set)