You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Discoid lupus erythematosus and explain in detail?
Discoid lupus erythematosus is the most common type of chronic cutaneous lupus (CCLE), an autoimmune skin condition on the lupus erythematosus spectrum of illnesses. It presents with red, painful, inflamed and coin-shaped patches of skin with a scaly and crusty appearance, most often on the scalp, cheeks, and ears. Hair loss may occur if the lesions are on the scalp. The lesions can then develop severe scarring, and the centre areas may appear lighter in color with a rim darker than the normal skin. These lesions can last for years without treatment.Patients with systemic lupus erythematous develop discoid lupus lesions with some frequency. However, patients who present initially with discoid lupus infrequently develop systemic lupus. Discoid lupus can be divided into localized, generalized, and childhood discoid lupus.The lesions are diagnosed by biopsy. Patients are first treated with sunscreen and topical steroids. If this does not work, an oral medication—most likely hydroxychloroquine or a related medication—can be tried.

Signs and symptoms
Morphology of lesions
Discoid lupus erythematosus (DLE) skin lesions first present as dull or purplish red, disc-shaped flat or raised and firm areas of skin. These lesions then develop increasing amounts of white, adherent scale. Finally, the lesions develop extensive scarring and/or atrophy, as well as pigment changes. They may also have overlying dried fluid, known as crust. On darker skin, the lesions often lose skin pigmentation in the center and develop increased, dark skin pigmentation around the rim. On lighter skin, the lesions often develop a gray color or have very little color change. More rarely, the lesions may be bright red and look like hives.

Location of lesions
The skin lesions are most often in sun-exposed areas localized above the neck, with favored sites being the scalp, bridge of the nose, upper cheeks, lower lip, and ear and hands  24% of patients also have lesions in the mouth (most often the palate), nose, eye, or vulva, which are all mucosal parts of the body.More rarely, patients may have lesions on the head and neck as well as the arms and trunk.

Special characteristics of some lesions
Scalp lesions
When discoid lupus is on the scalp, it starts as a red flat or raised area of skin that then loses hair and develops extensive scarring. The lesions often lose skin pigment and become white with areas of increased skin pigment, with or without areas of redness, and have a sunken appearance. They can have a smooth surface or have visible, dilated hair follicles on the surface.

Lip lesions
When discoid lupus is on the lip, it often has a grey or red colour with a thickened top layer of skin (known as hyperkeratosis), areas where the top layer has worn away (known as erosion), and a surrounding rim of redness.

Other symptoms
Patients may state that their lesions are itchy, tender, or asymptomatic. In addition to their skin lesions, they may also have swelling and redness around their eyes, as well as blepharitis.

Complications
Darker-skinned patients are often left with severe scarring and skin color changes even after the lesions get better. In addition, these patients have an increased, though still small, risk for aggressive skin squamous cell carcinoma.

Causes
Sun exposure triggers lesions in people with discoid lupus erythematous (DLE). Evidence does not clearly demonstrate a genetic component to DLE; however, genetics may predispose certain people to disease.

Mechanism
Most experts consider DLE an autoimmune disease since pathologists see antibodies when they biopsy the lesions and look at the tissue under the microscope. However, scientists do not understand the connection between these antibodies and the lesions seen in discoid lupus.Possibly, UV light damages skin cells, which then release material from their nuclei. This material diffuses to the dermoepidermal junction, where it binds to circulating antibodies, thereby leading to a series of inflammatory reactions by the immune system.Alternatively, dysfunctional T cells may lead to the disease.

Diagnosis
When a patient initially presents with discoid lupus, the doctor should ensure that the patient does not have systemic lupus erythematosus. The doctor will order tests to check for anti-nuclear antibodies in the patients serum, low white blood cell levels, and protein and/or blood in the urine.In order to help with diagnosis, the doctor may peel off the top layer of scale from a patients lesions in order to look at its underside. If the patients do indeed have discoid lupus, the doctor may see tiny spines of keratin that look like carpet tacks and are called langue au chat.Diagnosis is confirmed through biopsy. Typical biopsy findings include deposits of IgG and IgM antibodies at the dermoepidermal junction on direct immunofluorescence. This finding is 90% sensitive; however, false positives can occur with biopsies of facial lesions. In addition, pathologists often see groups of white blood cells, particularly T helper cells, around the follicles and blood vessels in the dermis. The epidermis appears thin and has effaced rete ridges as well as excess amounts of keratin clogging the openings of the follicles. The basal layer of the epidermis sometimes appears to have holes in it since some of the cells in this layer have broken apart. The remains of skin cells that have died through a process called apoptosis are visible in the upper layer of the dermis and the basal layer of the epidermis.The differential diagnosis includes actinic keratoses, sebborheic dermatitis, lupus vulgaris, sarcoidosis, drug rash, Bowens disease, lichen planus, tertiary syphilis, polymorphous light eruption, lymphocytic infiltration, psoriasis, and systemic lupus erythematosus.

Classification
Discoid lupus can be broadly classified into localized discoid lupus and generalized discoid lupus based on the location of the lesions. Patients who develop discoid lupus in childhood also have their own sub-type of disease.Hypertrophic lupus and lupus profundus are two special types of discoid lupus distinguished by their characteristic morphological findings.Finally, many patients with systemic lupus also develop discoid lupus lesions.

Localized
Most people with discoid lupus only have lesions above the neck and therefore have localized discoid lupus erythematosus.

Generalized
Rarely, patients may have lesions above and below the neck; these patients have generalized discoid lupus erythematosus. In addition to lesions in the typical above-the-neck locations, patients with generalized discoid lupus often have lesions on the thorax and the arms. These patients are often bald, with abnormal skin pigment on their scalp, and have severe scarring of the face and arms. Patients with generalized discoid lupus often have abnormal lab tests, such as an elevated ESR or a low white blood cell count. They also often have auto-antibodies, such as ANA or anti-ssDNA antibody.

Childhood
When patients develop discoid lupus in childhood, it differs from typical discoid lupus in several ways. Boys and girls are equally affected, and these patients later develop SLE more often. These patients also typically do not have any abnormal sensitivity to the sun.

Special types of discoid lupus lesions
Hypertrophic lupus
Some experts consider hypertrophic lupus erythematosus—which consists of lesions covered by a very thick, keratin-filled scale—an unusual subset of discoid lupus. Others consider it a distinct entity.

Lupus profundus
If a patient has discoid lupus lesions on top of lupus panniculitis, they have lupus profundus. These patients have firm, nontender nodules with defined borders underneath their discoid lupus lesions.

Systemic lupus erythematosus with discoid lupus lesions
In general, patients with discoid lupus who have only skin disease and no systemic symptoms have a genetically distinct disease from patients with SLE