Actinic prurigo (AP) is an uncommon kind of idiopathic photodermatosis that affects the skin’s sun-exposed parts the most. The afflicted skin areas are often the face, neck, and dorsal surface of the upper extremities. Sun-protected skin parts, such as the buttocks. Actinic prurigo often appears as symmetrically highly pruritic papulonodular dermatitis in the spring and can last throughout the winter. Excoriations, cheilitis, conjunctival illness, and scarring may develop in severe instances.

In severe and long-term cases, skin covered by clothing (e.g., buttocks) may also be damaged, making the effect of sunlight less visible. Furthermore, the illness frequently lingers throughout the year, although it is normally considerably worse in the summer.Actinic prurigo is also known as ‘Hutchinson prurigo’.

Symptoms of Actinic Prurigo

Skin Symptoms

• Affected Areas: The skin areas commonly affected include the face, neck, arms, hands, and legs.
• Type of Lesions: The symptoms manifest as itchy, inflammatory papules, nodules, and plaques.
• Onset Timing: These lesions generally appear hours or days after exposure to sunlight.
• Non-Sun-Exposed Lesions: Lesions can appear on skin areas that are covered by clothes and not directly exposed to UV rays. This unique aspect makes Actinic Prurigo especially difficult to diagnose accurately.

Specific Facial Areas

• Commonly Affected: Sun-exposed facial regions like cheeks, nose, forehead, chin, and earlobes are particularly vulnerable.
• Neck and Chest: The “V” region of the neck and upper chest is another common area.

Involvement of Lips and Eyes

• Lips: In 60–70% of Actinic Prurigo cases, the lips are involved. For 10% of patients, the lips may be the only affected site.
• Conjunctiva: The eye’s conjunctiva is affected in approximately 45% of cases.

Seasonal Fluctuations

• Chronic Nature: Actinic Prurigo is a chronic condition.
• Worsening in Spring and Summer: Symptoms typically worsen during the spring and summer seasons due to increased sun exposure.

Causes of Actinic Prurigo

Actinic prurigo develops when people are exposed to long- and short-wave ultraviolet radiation (UVA and UVB). The cause of this response between skin and sunlight is unclear.

Actinic prurigo may be an immunologically mediated hereditary illness, according to the current study, as some individuals have a family history of the disorder. Human Leukocyte Antigen (HLA) DRB1*0407 is more common among afflicted people, according to genetic research.

Risk Factors Associated With Actinic Prurigo

Demographics

AP is a familial dermatosis that mostly affects Native Americans and people of mixed ancestry (Mestizo) in the Americas, primarily in Central and South America. It appears to be more common in dryer, warmer areas over 1000 meters in elevation. There is some evidence that living with domestic and farm animals, as well as being exposed to wood smoke, are different risk factors. It has also been reported in White and Asian people. AP often manifests in youth, with onset occurring before the age of ten. In the Americas, there is about 4:1 female prevalence, but studies show a larger proportion of adult-onset cases with a male preponderance in Asian cultures.

Incidence Of Actinic Prurigo In Male And Female

There are no gender variations in frequency among children and adolescents. In adults, however, women are afflicted more commonly than males, with a female-to-male ratio of 2:1.

Diagnosis of Actinic prurigo

Actinic prurigo is often diagnosed clinically by a thorough history and physical examination. Patients will describe the typical symptoms of highly pruritic papulonodular erythematous skin lesions that started in the spring or summer. Patients may or may not report a direct link between sun exposure and illness. Skin photo-testing, histologic assessment, and genetic screening for the HLA DR4 allele variation can all help with diagnosis. To rule out lupus erythematosus and other photosensitive dermatoses, clinicians frequently undertake laboratory tests and immunofluorescence investigations.

Although a biopsy alone is insufficient to detect actinic prurigo, histopathology can aid in diagnosis and rule out other disease processes with comparable symptoms. Biopsies of the skin will reveal hyperkeratosis, spongiosis, and acanthosis in the epidermis, as well as lymphocytic perivascular infiltration in the dermis. A lip biopsy will reveal lymphoid germinal centers in the lamina propria, allowing actinic prurigo to be distinguished from the polymorphous mild eruption. In addition, studies have shown that eosinophils and mast cells infiltrate the underlying mucosa of afflicted lesions, which correlates with a delayed type-IVb hypersensitive response.

Treatment of Actinic prurigo

Some drugs have been used to treat actinic prurigo symptoms. These are some examples:

• Itching relief emollients.
• Corticosteroids used topically.
• Antimalarials have anti-inflammatory properties, such as hydroxychloroquine.
• Thalidomide – After improvement is shown, the medicine should be progressively lowered and ultimately discontinued. In the event of a relapse, it can be restarted. Because thalidomide might cause birth defects, it should be taken with caution, especially in women of reproductive age.

In some cases, actinic prurigo spontaneously resolves in early adult life. 

Side Effects Associated With Medicines

• Corticosteriods-Skin thinning, stretch marks, easy bruising, dilated blood vessels, and, less typically, increased hair growth are among symptoms that take weeks to months to develop.
• Hydroxychloroquine- weakness, cramps, stiffness or spasms, or changes in how your skin feels such as tingling.

Prevention

Actinic prurigo has no known cure. The basic objective is to avoid sun exposure as much as possible. Patients must understand that their illness will deteriorate during the hottest months of the year, and they must use sun protection techniques to minimize or limit breakouts

• Protect your skin with clothing. Ensure that you wear a hat that protects your face, neck, and ears, and a pair of UV-protective sunglasses.
• Make use of shade between 11 a.m. and 3 p.m. when it’s sunny.
• No sunscreen can offer you 100% protection. They should be used to provide additional protection from the sun, not as an alternative to clothing and shade.
• It may be worth taking vitamin D supplement tablets (available from health food stores) as strictly avoiding sunlight can reduce your vitamin D levels.
• Increasing intake of food rich in vitamin D such as oily fish, eggs, meat, fortified margarine, and cereals.

Common Misconceptions and Diagnostic Challenges

Potential for Confusion with Other Conditions

Misidentification Risk: Patients often mistake Actinic Prurigo for other skin conditions, complicating an accurate diagnosis.

Importance of Laboratory Tests

Necessity for Comprehensive Diagnosis: To confirm a diagnosis of Actinic Prurigo and rule out other conditions, laboratory tests are indispensable.

Commonly Confused Conditions

• Polymorphous Light Eruption: This is another skin condition triggered by sun exposure, and it can be easily confused with Actinic Prurigo.
• Systemic Lupus Erythematosus: This autoimmune disease can present with skin symptoms similar to Actinic Prurigo, further highlighting the need for laboratory tests.
• Porphyria: This group of disorders can also produce skin symptoms upon sun exposure, making it another potential source of diagnostic confusion.

Frequently Asked Questions (FAQs) about Actinic Prurigo