The disease can last for a considerably long time. Occasionally, "spontaneous cure" may ensue, particularly in young girls.

Lichen sclerosus is associated with a higher risk of cancer. Skin that has been scarred as a result of lichen sclerosus is more likely to develop skin cancer. Women with lichen sclerosus may develop vulvar carcinoma. Lichen sclerosus is associated with 3–7% of all cases of vulvar squamous cell carcinoma. In women, it has been reported that 33.6 times higher vulvar cancer risk is associated with LS. A study in men reported that "The reported incidence of penile carcinoma in patients with BXO is 2.6–5.8%".

In contrast to cutaneous LP, which is self limited, lichen planus lesions in the mouth may persist for many years, and tend to be difficult to treat, with relapses being common. Atrophic/erosive lichen planus is associated with a small risk of cancerous transformation, and so people with OLP tend to be monitored closely over time to detect any potential change early. Sometimes OLP can become secondarily infected with Candida organisms.

In 2016, interferon gamma/CXCL10 axis was hypothesized to be a target for treatments that reverse inflammation. Apremilast is undergoing investigation as a potential treatment .

Lichen sclerosus may have a genetic component. Higher rates of lichen sclerosus have been reported among twins and among family members.

Worldwide, KP affects an estimated 30-50% of the adult population and approximately 50-80% of all adolescents. It is more common in women than in men, and is often present in otherwise healthy individuals. The skin condition is prevalent in persons of all ethnicities. No particular ethnicity is at higher risk for developing keratosis pilaris. Although keratosis pilaris may manifest in persons of any age, it usually appears within the first decade of life and is more common in young children. In most cases, the condition gradually improves before age 30, however it can persist longer.

Fiddler’s neck does not usually form unless the musician is practicing or playing for more than a few hours each day, and only seems to develop after a few years of serious playing. Thus, when not infected or otherwise problematic, fiddler’s neck may be known as a benign practice mark and may be worn proudly as an indication of long hours of practice. Blum & Ritter (1990) found that 62% of 523 professional violinists and violists in West Germany experienced fiddler’s neck, with the percentage among violists being higher (67%) than among violinists (59%). Viola players are believed to be more predisposed to developing fiddler’s neck than violinists because the viola is larger and heavier, but this has not been empirically confirmed.

The development of fiddler’s neck does not depend on preexisting skin problems, and Blum & Ritter find that only 23% of men and 14% of women in their study reported cutaneous disorders in other parts of the face (mainly acne and eczema) that were independent of playing the violin or viola. Fiddler’s neck may exacerbate existing acne, but acne may also be limited solely to the lesion and not appear elsewhere. Nonetheless, musicians with underlying dermatologic diseases like acne and eczema are more endangered by fiddler’s neck than others. Males may develop folliculitis or boils due to involvement of beard hair.

The bacteria staphylococci are present in the majority of cases. Treatment with systemic antibiotics and coal tar shampoo can completely clear the condition when Staphylococcus aureus bacteria are found. Fungal infections such as tinea capitis are known to mimic the symptoms of the condition and can be cleared with antifungal treatment.

Lichen aureus (also known as "lichen purpuricus") is a skin condition characterized by the sudden appearance of one or several golden or rust-colored, closely packed macules or lichenoid papules.

Pemphigus foliaceus has been recognized in pet dogs, cats, and horses and is the most common autoimmune skin disease diagnosed in veterinary medicine. Pemphigus foliaceus in animals produces clusters of small vesicles that quickly evolve into pustules. Pustules may rupture, forming erosions or become crusted. Left untreated, pemphigus foliaceus in animals is life-threatening, leading to not only loss of condition but also secondary infection.

Pemphigus vulgaris is a very rare disorder described in pet dogs and cats. Paraneoplastic pemphigus has been identified in pet dogs.

Lichen nitidus is a chronic inflammatory disease of unknown cause characterized by 1–2 mm, discrete and uniform, shiny, flat-topped, pale flesh-colored or reddish-brown papules that may appear as hypopigmented against dark skin. Occasionally, minimal scaling is present or can be induced by rubbing the surface of the papules. The disease usually affects children and young adults and is painless and usually nonpruritic, although protracted itching may occur in some cases. It is sometimes referred to by dermatologists as "mini lichen planus".

Lichen scrofulosorum (also known as "Tuberculosis cutis lichenoides") is a rare tuberculid that presents as a lichenoid eruption of minute papules in children and adolescents with tuberculosis. The lesions are usually asymptomatic, closely grouped, skin-colored to reddish-brown papules, often perifollicular and are mainly found on the abdomen, chest, back, and proximal parts of the limbs. The eruption is usually associated with a strongly positive tuberculin reaction.

Of the three tuberculids, the incidence of lichen scrofulosorum was found to be the lowest (2%) in a large study conducted in Hong Kong. This highlights its rarity and significance as an important marker of undetected tuberculosis.

Generally, lichen nitidus is asymptomatic and self-limited; therefore, no treatment is required. However, if persistent pruritus is present, or the appearance “...interferes with daily activities or outlook...” topical glucocorticoids may be tried. If the disease process is symptomatic, generalized and extensive, oral glucocorticoids may be indicated. Other reported treatments include PUVA, UVA/UVB phototherapy, astemizole, acitretin, and etretinate.

When appears with sun/humidity; air conditioning (cool dry air) reduces swelling and discomfort.

Keratosis pilaris occurs when the human body produces excess amounts of the skin protein keratin, resulting in the formation of small, raised bumps in the skin often with surrounding redness. The excess keratin, which is the color of the person's natural skin tone, surrounds and entraps the hair follicles in the pore. This causes the formation of hard plugs (process known as hyperkeratinization). Many KP bumps contain an ingrown hair that has coiled. This is a result of the keratinized skin's "capping off" the hair follicle, preventing the hair from exiting. The hair grows encapsulated inside the follicle. KP is more common in patients affected by atopic diseases such as allergic rhinitis and atopic dermatitis.

The cause of prurigo nodularis is unknown, although other conditions may induce PN. PN has been linked to Becker's nevus, linear IgA disease, an autoimmune condition, liver disease and T cells. Systemic pruritus has been linked to cholestasis, thyroid disease, polycythaemia rubra vera, uraemia, Hodgkins disease, HIV and other immunodeficiency diseases. Internal malignancies, liver failure, renal failure, and psychiatric illnesses have been considered to induce PN, although more recent research has refuted a psychiatric cause for PN. Patients report an ongoing battle to distinguish themselves from those with psychiatric disorders such as delusions of parasitosis and other psychiatric conditions.

Pityriasis amiantacea (also known as "Tinea amiantacea") is an eczematous condition of the scalp in which thick tenaciously adherent scale infiltrates and surrounds the base of a group of scalp hairs. It does not result in scarring or alopecia.

Pityriasis amiantacea was first described by Alibert in 1832. Pityriasis amiantacea affects the scalp as shiny asbestos-like (amiantaceus) thick scales attached in layers to the hair shaft. The scales surround and bind down tufts of hair. The condition can be localised or covering over the entire scalp. Temporary alopecia and scarring alopecia may occur due to repeated removal of hairs attached to the scale. It is a rare disease with a female predilection.

Pityriasis amiantacea can easily be misdiagnosed due its close resemblance to other scalp diseases such as psoriasis, seborrhoeic dermatitis or lichen planus. However in pityriasis amiantacea the scales are attached to both the hair shaft and the scalp. Pityriasis amiantacea may be present with other inflammatory conditions such as atopic dermatitis or seborrhoeic dermatitis and sebaceous scales and alopecia can occur. According to the dermatology text Bolognia this condition is most often seen in psoriasis, but may also be seen in secondarily infected atopic dermatitis, seborrheic dermatitis, and tinea capitis.

Lichen striatus (also known as blaschko linear acquired inflammatory skin eruption and linear lichenoid dermatosis) is a rare skin condition that is seen primarily in children, most frequently appearing ages 5–15. It consists of a self-limiting eruption of small, scaly papules.

A papulosquamous disorder is a condition which presents with both papules and scales, or both scaly papules and plaques.

Examples include psoriasis, lichen planus, and pityriasis rosea.

Chronic and repetitive scratching, picking, or rubbing of the nodules may result in permanent changes to the skin, including nodular lichenification, hyperkeratosis, hyperpigmentation, and skin thickening. Unhealed, excoriated lesions are often scaly, crusted or scabbed. Many patients report a lack of wound healing even when medications relieve the itching and subsequent scratching.

Patients often:

- seek treatment during middle-age, although PN can occur at any age.

- have a history of chronic severe pruritus.

- have a significant medical history for unrelated conditions.

- suffer from liver or kidney dysfunctions.

- suffer secondary skin infections.

- have a personal or family history of atopic dermatitis.

- have other autoimmune disorders.

- have low vitamin D levels.

There are many skin diseases which develop papules, such as Lichen planus, a skin disease which classically forms polygonal, purple papules.

The proximal causes of fiddler’s neck are friction and pressure, but both repetitive shearing stress and occlusion with consequent trapping of sweat give rise to progressive damage. This damage along with poor hygiene predisposes the area to local infection, and such infection can progress to scarring and other long-term effects. Hot weather is reported to exacerbate fiddler’s neck, as are tiredness, playing emotional music, and playing in smaller groups where individual stress is higher. Type I hypersensitivity reactions may also be involved, particularly to rosewood and ebony in the chinrest and tailpiece, as well as to varnish of the instrument body when chinrests are not used and to rosin deposits on the instrument and on chin cloths. Nickel or other metal allergies are common causes if the chin rest has a metal clip that comes into constant contact with the skin. Rosin exposure in particular may lead to abietic acid dermatitis.

Keratosis pilaris atrophicans faciei (also known as "Folliculitis rubra," "Keratosis pilaris rubra atrophicans faciei," "Lichen pilare," "Lichen pilaire ou xerodermie pilaire symetrique de la face," "Ulerythema ophryogenes," and "Xerodermie pilaire symetrique de la face") begins in infancy as follicular papules with perifollicular erythema. Initially, the lesions are restricted to the lateral eyebrows, but with time spread to involve the cheeks and forehead, and may also be associated with keratosis pilaris on the extremities and buttocks.

Many conditions affect the human integumentary system—the organ system covering the entire surface of the body and composed of skin, hair, nails, and related muscle and glands. The major function of this system is as a barrier against the external environment. The skin weighs an average of four kilograms, covers an area of two square meters, and is made of three distinct layers: the epidermis, dermis, and subcutaneous tissue. The two main types of human skin are: glabrous skin, the hairless skin on the palms and soles (also referred to as the "palmoplantar" surfaces), and hair-bearing skin. Within the latter type, the hairs occur in structures called pilosebaceous units, each with hair follicle, sebaceous gland, and associated arrector pili muscle. In the embryo, the epidermis, hair, and glands form from the ectoderm, which is chemically influenced by the underlying mesoderm that forms the dermis and subcutaneous tissues.

The epidermis is the most superficial layer of skin, a squamous epithelium with several strata: the stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale. Nourishment is provided to these layers by diffusion from the dermis, since the epidermis is without direct blood supply. The epidermis contains four cell types: keratinocytes, melanocytes, Langerhans cells, and Merkel cells. Of these, keratinocytes are the major component, constituting roughly 95 percent of the epidermis. This stratified squamous epithelium is maintained by cell division within the stratum basale, in which differentiating cells slowly displace outwards through the stratum spinosum to the stratum corneum, where cells are continually shed from the surface. In normal skin, the rate of production equals the rate of loss; about two weeks are needed for a cell to migrate from the basal cell layer to the top of the granular cell layer, and an additional two weeks to cross the stratum corneum.

The dermis is the layer of skin between the epidermis and subcutaneous tissue, and comprises two sections, the papillary dermis and the reticular dermis. The superficial papillary dermis with the overlying rete ridges of the epidermis, between which the two layers interact through the basement membrane zone. Structural components of the dermis are collagen, elastic fibers, and ground substance. Within these components are the pilosebaceous units, arrector pili muscles, and the eccrine and apocrine glands. The dermis contains two vascular networks that run parallel to the skin surface—one superficial and one deep plexus—which are connected by vertical communicating vessels. The function of blood vessels within the dermis is fourfold: to supply nutrition, to regulate temperature, to modulate inflammation, and to participate in wound healing.

The subcutaneous tissue is a layer of fat between the dermis and underlying fascia. This tissue may be further divided into two components, the actual fatty layer, or panniculus adiposus, and a deeper vestigial layer of muscle, the panniculus carnosus. The main cellular component of this tissue is the adipocyte, or fat cell. The structure of this tissue is composed of septal (i.e. linear strands) and lobular compartments, which differ in microscopic appearance. Functionally, the subcutaneous fat insulates the body, absorbs trauma, and serves as a reserve energy source.

Conditions of the human integumentary system constitute a broad spectrum of diseases, also known as dermatoses, as well as many nonpathologic states (like, in certain circumstances, melanonychia and racquet nails). While only a small number of skin diseases account for most visits to the physician, thousands of skin conditions have been described. Classification of these conditions often presents many nosological challenges, since underlying etiologies and pathogenetics are often not known. Therefore, most current textbooks present a classification based on location (for example, conditions of the mucous membrane), morphology (chronic blistering conditions), etiology (skin conditions resulting from physical factors), and so on. Clinically, the diagnosis of any particular skin condition is made by gathering pertinent information regarding the presenting skin lesion(s), including the location (such as arms, head, legs), symptoms (pruritus, pain), duration (acute or chronic), arrangement (solitary, generalized, annular, linear), morphology (macules, papules, vesicles), and color (red, blue, brown, black, white, yellow). Diagnosis of many conditions often also requires a skin biopsy which yields histologic information that can be correlated with the clinical presentation and any laboratory data.

Therapy for cutaneous tuberculosis is the same as for systemic tuberculosis, and usually consists of a 4-drug regimen, i.e., isoniazid, rifampin, pyrazinamide, and ethambutol or streptomycin.

Tuberculosis verrucosa cutis (also known as "lupus verrucosus", "prosector's wart", and "warty tuberculosis") is a rash of small, red papular nodules in the skin that may appear 2–4 weeks after inoculation by "Mycobacterium tuberculosis" in a previously infected and immunocompetent individual.

It is so called because it was a common occupational disease of prosectors, the preparers of dissections and autopsies. Reinfection by tuberculosis via the skin, therefore, can result from accidental exposure to human tuberculous tissue in physicians, pathologists and laboratory workers; or to tissues of other infected animals, in veterinarians, butchers, etc. Other names given to this form of skin tuberculosis are anatomist's wart and verruca necrogenica (literally, generated by corpses).

TVC is one of the many forms of cutaneous tuberculosis, such as the tuberculous chancre (which results from the inoculation in people without immunity), and the reactivation cutaneous tuberculosis (the most common form, which appears in previously infected patients). Other forms of cutaneous tuberculosis are: lupus vulgaris, scrofuloderma, lichen scrofulosorum, erythema induratum and the papulonecrotic tuberculid.

It was described by René Laennec in 1826.

Papular mucinosis affects adults of both sexes equally and appears between ages 30 and 80. Recently, it has been reported in patients infected with the HIV/AIDS virus.