What is chronic actinic dermatitis? How to treat chronic actinic dermatitis?

Chronic actinic dermatitis is a common skin disease that occurs frequently in middle-aged and elderly people and is easily misdiagnosed as eczema or neurodermatitis. So what is the cause of chronic actinic dermatitis? How to treat it?

Causes

The pathogenic spectrum of this disease includes medium and long wave ultraviolet rays and visible light, and the cause of the disease is still unknown. Clinical, histopathological and immunohistochemical results all suggest that this disease is a delayed hypersensitivity reaction. Common photosensitizers that act as allergens include certain plant ingredients, spices and photosensitizing drugs.

Clinical manifestations

Diffuse bright red slightly edematous macules, with scattered red papules and mild exudation, presenting as dermatitis eczematous lesions. This is followed by infiltrated and thickened lichenoid papules and plaques with a small amount of scales on the surface, dark red in color, and clear boundaries. There are plaques formed by fusion of nodules on the forehead or mastoid area. The nodules reduce the wrinkles of loose skin and give it a translucent appearance. Facial lesions may appear lion-like.

Skin lesions are prone to occur on exposed areas such as the face, neck, and back of the hands. The neck is most common on the sides and back of the neck near the posterior mastoid process. In male patients, the sparse hair area on the top of the head is often affected, and the extensor side of the forearm is also common. Non-exposed parts can also be affected. In severe cases, there may occasionally be a tendency towards erythroderma.

90% of the patients are male, 90% are between 50 and 75 years old, and it is rare for those under 50 years old. Outdoor workers have a higher incidence rate. Most patients are Caucasians, but cases have also been reported in blacks and Asians.

Many patients have a long medical history, but often cannot provide a clear history of photoinduced dermatitis and frequent attacks in summer. It is often unclear whether contact allergy is caused by certain specific allergens. However, despite this, contact allergy and photosensitivity reactions exist at the same time.

The course of this disease is chronic, and the skin lesions often do not heal throughout the year.

diagnosis

①Persistent dermatitis or eczematous skin lesions, which may be accompanied by infiltrative papules and plaques. ① The exposed area is mainly affected or may extend to other places, occasionally presenting as erythroderma; ② The minimum erythema dose measurement is abnormally sensitive to UVB, and some are also sensitive to UVA and visible light. The light stimulation test and spot test may be positive; ③ The histopathological changes are similar to chronic eczema and (or) pseudolymphoma.

Differential diagnosis:

(I) General dermatitis and eczema-like diseases without a clear history of photosensitivity; the skin lesions are distributed symmetrically or mainly at the contact sites, and the minimum erythema dose measurement shows no abnormal reaction to UVB.

(ii) Temporary photosensitivity reaction refers to exogenous photosensitivity contact dermatitis and photosensitivity drug rash. Photosensitivity reaction still occurs within 1-2 weeks after avoiding photosensitizers, and then it can quickly improve and heal. There is no persistent photosensitivity. During this period, the patient may be abnormally sensitive to UVA, with a positive patch test, but the sensitivity to UVB is normal.

(III) Polymorphous light eruption has a clear history of photosensitivity. The disease presents with acute intermittent attacks, obvious seasonality and fluctuation, and is more common in young and middle-aged women. Photobiological tests are generally negative, but a few are also sensitive to UVB and/or UVA.

Laboratory examination: ① Light test: Use single wavelength light to irradiate non-exposed skin without skin lesions, showing abnormal sensitivity to UVB (wavelength 280-315nm) and UVA (wavelength 315-400nm), and occasionally sensitive to visible light (wavelength above 400 nm). ②Light spot test: Some patients show positive reactions to certain contact photosensitizers and suspected photosensitizers.

Prevention and treatment

Try to identify and avoid possible contact allergens and contact with and taking various products and medicines containing photosensitizers. Strictly avoid sunlight exposure, and highly sensitive people can only use incandescent lamps or live and work in a dark room. A sunscreen with a broad spectrum of coverage for external use. Wear a wide-brimmed hat and long-sleeved clothes when going out.

Oral nicotinamide, hydroxychloroquine, supplemented with antihistamines and B vitamins. During the acute exacerbation period, small doses of glucocorticoids or tripterygium wilfordii preparations can be added to control the condition. For severe patients, thalidomide can be used.

Local treatment generally uses glucocorticoid preparations, topical tacrolimus, and local cold spray treatment on the face.

Traditional Chinese medicine can dispel wind and heat, promote blood circulation and remove blood stasis. You can use Schizonepeta, Saposhnikovia, Honeysuckle, Forsythia, Rehmannia, Salvia miltiorrhiza, Scrophularia, etc.