Actinic Keratosis Differential Diagnosis Table

Actinic Keratosis Differential Diagnosis Table:

Actinic Keratosis or solar keratosis is a premalignant condition in which the skin becomes dry, rough, and scaly patches appear on the upper layer of the skin due to long-term exposure to the sun. Symptoms are flat to raised bumps on the upper layer of the skin, which sometimes turn hard, small, rough, or scaly patch, color changes are skin-colored, red, and pink. Occasionally, itching and burning cause bleeding or crusting.
Risk factors include male gender,age more than 40 years,immunocompromised,fair skin tone,light coloured eyes,albinism,excessive exposure to sun rays.
Risk factors include male gender, age more than 40 years, immunocompromised, fair skin tone, light-colored eyes, albinism, excessive exposure to sun rays. Actinic keratosis is caused by long-term exposure to UV radiations of the sun. It mostly develops on sun-exposed areas, and fair skin is more prone to develop this disease. It can revert, remain stable, or cause dysplasia resulting in other skin cancers, mainly squamous cell carcinoma.
It is diagnosed by history and examination of the affected area. Other methods that help in diagnosis are biopsy, dermoscopy, examination under a microscope, and optical coherence tomography. Treatment options include cryosurgery to freeze the lesion, curettage, chemical peeling to remove the upper layer of skin, laser resurfacing, and photodynamic therapy.

How to Distinguish Actinic Keratosis from Other Diseases

Distinguish Psoriasis Vulgaris from Actinic Keratosis – Diagnosis

Psoriasis Vulgaris is a long-lasting skin condition in which the skin becomes dry, thick, and silvery white patches (scales) are formed on the skin. It shows peaks and valleys in the course. The skin can cause itching and soreness. The symptoms that distinguish psoriasis vulgaris from actinic keratosis are:

• Psoriasis Vulgaris is caused on the skin where there is frequent injury or friction of the skin, resulting in more rapid replacement of the epidermis, while actinic keratosis is caused by exposure to UV rays.
• Both diseases can occur anywhere, but the former is more common on the scalp, knees, elbows, and lower back, while the latter is common in sun-exposed areas like the face, hands, scalp, and chest.
• Both diseases, due to their raised reddish spots, look similar, but the former is usually soft yet dry while the latter is rough and crusty.

Psoriasis can be diagnosed on skin examination and confirmed on skin biopsy. Treatment options include topical steroid creams and ointments, oral or IV corticosteroids, and phototherapy.

Distinguish Contact Dermatitis from Actinic Keratosis – Diagnosis

It is a type of eczema that forms a non-contagious itchy rash caused by an allergic reaction to a substance when it comes in direct contact with the skin. It forms an itchy rash, bumps, and blisters, hyperpigmented patches on dark skin, and dry and scaly patches on fair skin tone, sometimes with burning, pain, and inflammation. The symptoms that distinguish contact dermatitis from actinic keratosis are:

• Contact dermatitis is caused anywhere on the body where an allergic substance touches the skin, while actinic keratosis is mainly caused on sun-exposed parts of the body.
• Contact dermatitis is an immediate reaction occurring within a few hours to days after exposure to an irritant or an allergic substance, while actinic keratosis is caused by years or decades of exposure to the sun.
• Contact dermatitis heals within days or weeks, while actinic keratosis can regress, remain stable, or progress to squamous cell carcinoma.

Contact dermatitis is diagnosed based on history and clinical examination. Patch testing is the gold standard test for diagnosis. Treatment options include protection from irritants or allergens, topical or oral anti-itch creams, and medicines.

Distinguish Basal Cell Carcinoma from Actinic Keratosis – Diagnosis

Basal cell carcinoma is the most common, locally invasive, slow-growing tumor caused by long-term exposure to UV rays of the sun. Symptoms are pearly or dome-shaped lesions, itching, extreme sensitivity to light, and often bleeding. The features that distinguish BCC from Actinic keratosis are:

• BCC is the most common type of skin cancer, while actinic keratosis is a pre-malignant condition that can lead to squamous cell carcinoma.
• BCC presents with sores that often ooze and don’t heal, while actinic keratosis doesn’t have sores.
• Both cases have lesions that are hard to differentiate, but BCC lesion has rolled edges with central depression, while actinic keratosis has a flat to raised patch with no central depression.

BCC is diagnosed based on history and examination, while skin biopsy is done to confirm the diagnosis. Topical medication and surgical removal have proven effective in treating BCC.

Distinguish Squamous Cell Carcinoma from Actinic Keratosis – Diagnosis

Squamous cell carcinoma is a common type of skin cancer caused by the overproliferation of squamous cells in the upper and middle layers of the skin. It appears as a dry and crusted sore or irregular ulcer with an everted margin. The features that distinguish squamous cells from actinic keratosis are:

• Squamous cell carcinoma originates from squamous cells in the superficial layer of the epidermis, while actinic keratosis involves the innermost layer of the epidermis.
• Squamous cell carcinoma metastasizes to internal organs like the lungs, thyroid, lymph nodes, and esophagus, while actinic keratosis can’t metastasize.
• Actinic Keratosis is a precancerous lesion that can develop into squamous cell carcinoma.
• Both tumors are found in sun-exposed areas, but the former invades the dermis while the latter has a hard and scaly surface without dermal infiltration.

Squamous cell carcinoma is diagnosed based on history and examination; skin biopsy to confirm the diagnosis can also be performed. Surgery and radiotherapy are useful in treatment.

Distinguish Seborrheic Keratosis from Actinic Keratosis – Diagnosis

Seborrheic keratosis is a benign growth on the skin caused by the overgrowth of Amyloid Precursor Protein (APP). It appears as a painless, well-defined, waxy, and dark-colored raised bump. It shows signs of skin aging. The features that distinguish seborrheic keratosis from actinic keratosis are:

• Seborrheic keratosis is caused by the overexpression of APP, while actinic keratosis is caused by damage to keratinocyte DNA due to exposure to the sun or tanning beds.
• Seborrheic Keratosis is a dark round or oval bump that is adherent to the skin, while actinic keratosis is a flat to raised dry and scaly patch that forms crust and often bleeds on scratching.
• Both of the diseases can be treated and cured successfully, but the former is a non-cancerous lesion and is treated due to cosmetic reasons, while the latter has a tendency to progress into cancer in certain cases.

It is mainly diagnosed on clinical examination while skin biopsy can also be performed. It doesn’t require any treatment but can be removed for cosmetic reasons.

Distinguish Solar Lentigo from Actinic Keratosis – Diagnosis

Solar Lentigo is a disease caused in older people due to exposure to sunlight. Exposure to UV rays causes overproduction of melanocytes, which results in the deposition of melanin in skin cells. It appears as dark pigmented areas on the skin. The features that distinguish solar lentigo from actinic keratosis are:

• Both are caused by exposure to the sun, but the former are flat spots that appear as darker skin in the center with the normal color of skin in the periphery, while the latter appears as more thick and scaly patches of skin.
• Solar lentigo is smooth while actinic keratosis is dry and rough.
• Though both diseases are harmless, the latter can progress into Squamous cell carcinoma over time.

Solar lentigo is diagnosed by simply looking at it. It usually fades away with time, but chemical peeling, laser therapy, and cryotherapy are good treatment options.

Distinguish Bowen’s Disease from Actinic Keratosis – Diagnosis

Bowen’s disease or Squamous cell carcinoma in situ is a slow-growing, malignant, intraepidermal carcinoma. Symptoms are a flat to raised patch of red or pink color that may be scaly or form crust over time. The features that distinguish Bowen’s disease from actinic keratosis are:

• Both diseases, due to their clinical similarity, are hard to diagnose, but the former has large, red-colored scaly patches while the latter has small, red-colored raised scaly patches.
• On staining, Bowen’s disease stains the full thickness of the epidermis while sparing the basal layer, while in actinic keratosis staining occurs in the lower portion of the epidermis, including the basal layer.
• Bowen’s Disease is known to be an early stage of Squamous cell carcinoma while actinic keratosis is a pre-cancerous lesion that may or may not develop into carcinoma.

Biopsy is usually needed to detect Bowen’s disease. Surgical removal is considered to be the standard treatment for this disease.

Distingusih Lichen Planus from Actinic Keratosis – Diagnosis

Lichen Planus is a non-infectious, subacute, or chronic autoimmune disease of the skin and mucous membrane characterized by slightly raised, shiny, reddish-purple papules with a flat top. It can also cause itching, burning, and soreness. The symptoms that distinguish lichen planus from actinic keratosis are:

• Lichen planus cause is still unknown, but studies have shown it might be an autoimmune disease while actinic keratosis is a premalignant lesion.
• Lichen planus affects the skin, wrists, ankles, nails, scalp, and genital area while actinic keratosis is mostly present on sun-exposed areas of the body.
• Lichen planus presents as reddish-purple papules, polygonal with flat tops, and plaques having a white streak while actinic keratosis presents as flat to raised, dry and scaly patches on the skin that are pink, red, or dark in color.

Clinical examination and biopsy are helpful to diagnose lichen planus. Oral or topical steroids are helpful to reduce inflammation while light therapy can also be used.

Distinguish Lupus Erythematosus from Actinic Keratosis – Diagnosis

Lupus Erythematosus is a chronic inflammatory disease caused by autoimmune or environmental factors. It affects different organs of the body. Symptoms include fever, myalgias, arthralgias, sores, rashes, and UV light sensitivity. The features that differentiate lupus erythematosus from actinic keratosis are:

• Lupus erythematosus has a butterfly-shaped rash while actinic keratosis appears as rough, scaly patches.
• Although both lesions are hard to differentiate, the former has deep scarring while the latter rarely leaves a scar.
• Lupus Erythematosus can affect the lungs, heart, kidneys, joints, skin, brain, and blood vessels while actinic keratosis is limited to the skin. In rare cases, it can spread to surrounding tissues.

Lupus is diagnosed based on history, physical examination, blood tests for specific antibodies, biopsy, and urine tests. Anti-inflammatory drugs, immunosuppressants, corticosteroids, and lifestyle modifications can help in treating lupus erythematosus.

Red Flags of Actinic Keratosis

Although actinic keratosis is harmless and regresses with time, in certain cases it can lead to Squamous Cell Carcinoma of the skin, so one should take care if the following symptoms appear with actinic keratosis:

• Bleeding, Itching, Burning, and Blisters.
• When the lesion is rapidly growing and becomes painful.
• In immunocompromised people or with long-term use of immunosuppressants.
• Past history of skin cancer.