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Immunologically Mediated (Idiopathic) Photodermatoses by Mind Map: Immunologically
Mediated
 (Idiopathic)
Photodermatoses
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Immunologically Mediated (Idiopathic) Photodermatoses

Solar Urticaria

Action Spectrum

Visible light

Positive photo-testing with visible light (e.g., slide projector lamp) is diagnostic value

Type I Hypersensitivity Reaction

Clinical Presentation

Wheals start within (up to 30) minutes of sun exposure and last < 24 hours

Usually Females during 4th and 5th decade of life

May progress to anaphylactoid reaction

Associations

Atopic Dermatitis (up to 50%)

Erythropoetic Protoporphiria (EPP)

Lupus Erythematous

Medications

Therefore, test for LE and EPP in patients with solar urticaria

Negative test results seen in PMLE, AP, and CAD

Variants

Fixed SU, Limited to specific area on the body

Drug-Induced SU, Chlorpromazine, Tetracycline

Therapy

Photoprotection, Antihistamines, Low-Dose UVA, PUVA,

IVIG (in difficult cases)

Chronic Actinic Dermatitis (CAD)

3 Main Criteria:

Reduction in the MED to UVA, UVB and/or visible light, The hallmark of CAD is a lowered MEDB, Only CAD has lowered MEDB, distinguishing it from photoallergic contact dermatitis, So any board question with lower MEDB is most likely to be related to CAD

Photo-distribution

Pathology c/w AD with/without CTCL-like changes

Action Spectrum

UVB

DTH Type IV reaction (i.e., photoallergic)

Clinical Presentation

Usually men > 50 y/o (all races)

Initial symptom: persistent erythema of the face

Allergic and/or photoallergic contact dermatitis commonly coexist with CAD and often precedes the onset of photosensitivity

Positive patch testing, Sesquiterpene lactone mix, Compositae in UK patients

Treatment

Photoprotection, Allergen Avoidance, Azathioprine, CYS-A, MMF, Low Dose PUVA, topical Tacrolimus

CAD in younger individuals infected with HIV has recently been described

Hydroa Vacciniforme (HV)

Rare, chronic photodermatosis

Clinical Presentation

Occurring predominantly during the childhood (3-15 y/o; remits in adolescence)

Umbilicated vesicles in sun-exposed areas

appear within 30 minutes to 2 hours after sun exposure

Heal with vacciniform (varioliform) scars

May be accompanied by keratoconjuctivitis, photophobia, and constitutional symptoms

Boys tend to have longer course

Action Spectrum

UVA (most commonly)

Treatment

Photoprotection, NB-UVB, PUVA

Hydroa Vacciniforme-Like Lymphoma

While some researchers claim that HV can evolve into T-cell lymphoma, most insist that this is a disease distinct from the classical HV.

Severe forms of HV-like eruptions have been linked with an aggressive type of T-cell lymphoma

EBV-associated

mainly found in children from Asia and Latin America

Actinic Prurigo (AP)

Two variants

General Variant (Hutchinson’s Summer Prurigo):, May present a persistent variant of PMLE that occurs in genetically susceptible individuals, starts in childhood and resolves in adolescence, Girls > Boys, Usually European Countries (temperate climate), Worse in summer (rarely in other seasons)

Familial PMLE of Native Americans, Girls = Boys, Persists into adulthood (F>M), Skin photo-types IV and V, Occurs year-round

Clinically different than PMLE:

HLA DRB1*0407 marker distinguishes it from PMLE

Can involve photo-protected skin areas

Intensely pruritic, excoriated/lichenified papules and nodules with hemorrhagic crust that last longer than PMLE

Persists into winter

Cheilitis and Conjunctivitis are common (use eye protection)

Treatment: Thalidomide, Sun Glasses and Photoprotection, NB-UVB

Polymorphous Light Eruption (PMLE)

UVA is the most common action spectrum

Reproduction of lesions by photo-testing is of diagnostic value

Normal MED A/B

Skin phototypes I-IV

F>M

DTH response (Type IV Hypersensitivity) to a photo-induced antigen.

Clinical Presentation

Usually 2nd-3rd decade of life

Spring and early summer months in temperate climates

Presents minutes to hours (rarely days) after exposure to sunlight or artificial UVR (even visible light

Exclusively photo-distributed

Monomorphic papules, vesicles, and EM-like targetoid lesions

Eczematous and papular forms are the most common

No relation to a photo-sensitizing medication

Self limited due to “UV Hardening”: lasts for one to several days (occasionally weeks)

Treatment:

Sun avoidance, sunscreens and sun-protective clothing.

Sever cases: UV hardening, antimalarials, and prednisone.