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CHRONIC ACTINIC DERMATITIS

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DEFINITION:

It is a common eczematous photodermatosis i.e., an itchy, inflammatory skin disorder caused due to sun exposure persisting for long term.

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ETIOLOGY:Action Spectrum- UVA, UVB, Visible light.PREDISPOSING CONDITIONS: Allergic contact dermatitis Drug induced photosensitivity Endogenous eczema Air borne contact dermatitis HIV Infection Photoaged and aged skin.

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PATHOGENESIS: Presence of predominantly CD8+

cytotoxic suppressor cells results in developing CAD from pre existing disorders.

CAD may develop as delayed type of hypersensitivity reaction during initial localized photo allergic reaction to a normal skin altered to become antigenic by light or hapten binding to endogenous carrier protein through UVA dependent covalent photochemical reaction. DNA is the prime target.

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DNA of normal skin

cells

Altered to become an

antigen

Delayed type of

Hypersensitivity reaction

UV Radiati

on

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CLINICAL FEATURES: Itchy, confluent eczematous patches

seen over photo exposed sites Often a sharp border at the edge of

clothing Sparing of upper eyelids,

retroauricular and submental region, finger webs, depth of skin creases.

Erythematous plaques with shiny infiltrated papules may develop.

Lichenification over period of time.

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VARIANTS: Actinic Reticuloid Persistent light reactors Photosensitivity Dermatitis and EczemaDIAGNOSIS: Based on Clinical examination Histology-chronic eczema with or without

lymphoma like changes. Photobiologic- reduction in MED of UVB,

UVA on normal skin.

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DIFFERENTIAL DIAGNOSIS

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INVESTIGATIONS: Histopathology: In mild cases- chronic eczema, acanthosis

and spongiosis are seen. In severe CAD Pautrier like microabcesses

seen in epidermis. An upper dermal dense lymphocytic

perivascular infiltration seen. Eosinophils, macrophages, plasma cells

may be present. In Actinic Reticuloid it resembles T cell

lymphoma except mitotic figures are less frequent.

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PHOTO TESTING: Photo provocation is performed on uninvolved skin. An eczematous response to UVB in majority and to UVA,VR in less patients.The MED of UVB is reduced in 70% & UVA in 33% of patients. PATCH TEST and PHOTOPATCH TEST: To detect allergens like oleoresins, compositae sunscreens etc.

Blood tests:

Circulating Antinuclear antibodies. CD8+ sezary cells in the absence of malignancy.

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TREATMENT: Absolute photoprotection . Usage of broad spectrum sunscreens. Topical steroids in mild cases. Topical use of Tacrolimus. In moderate to severe cases: Azathioprine- 1.5 to 2.5 mg/kg/day Cyclosporine- 3.5 to 5 mg/kg/day PUVA therapy

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