Chronic actinic dermatitis
Although the etiology is unclear, one proposed pathophysiologic mechanism is that CAD results from photoinduced modification of endogenous cutaneous antigen(s).
CAD is most commonly seen in men aged older than 50 years, with a long history of either occupational or recreational outdoor activities. The condition can be seen in women and also rarely in younger patients. Affected patients of all ages often have a history of atopic dermatitis and/or a history of allergic contact dermatitis and thus have a baseline tendency for delayed-type hypersensitivity reactions. CAD can occur in any skin type and anywhere in the world, although it is more commonly seen in patients with Fitzpatrick skin types V and VI and in temperate climates.
CAD may be a presenting sign of HIV infection, especially in younger CAD patients. If the diagnosis of CAD is considered, testing for HIV is recommended for patients with positive risk factors for HIV.
L57.1 – Actinic reticuloid
52636001 – Actinic reticuloid
- Polymorphous light eruption – Occurs in younger patients and in discrete attacks with clearance of lesions between flares.
- Photoexacerbated drug eruption – Usually appears more edematous and erythematous, but chronic cases may have lichenification. Check the patient's medication list for potential causes.
- Acute / subacute cutaneous lupus erythematosus – Malar distribution or polycyclic erythematous scaly plaques, usually not lichenified.
- Porphyrias (see porphyria cutanea tarda, variegate porphyria) – Can mimic this disease; rule out with stool / urine / serum porphyrins as appropriate.
- Mycosis fungoides – Not confined to photoexposed skin (although there is a rare photosensitive form of mycosis fungoides, and spillover to nonexposed sites can occur in CAD).
- Pellagra – May present similarly to CAD. The classic symptoms of diarrhea and dementia may or may not coincide. Check serum niacin levels if there are pellagra risk factors such as a history of alcohol use disorder.