Lichen planus (LP) is a chronic inflammatory and autoimmune disease that affects the skin, nails, hair, and mucous membranes. It is not an actual lichen, but is named for its appearance. It is characterized by polygonal, flat-topped, violaceous papules and plaques with overlying, reticulated, fine white scale, commonly affecting dorsal hands, flexural wrists and forearms, trunk, anterior lower legs and oral mucosa. The hue may be gray-brown in people with darker skin. Although there is a broad clinical range of LP manifestations, the skin and oral cavity remain as the major sites of involvement. The cause is unknown, but it is thought to be the result of an autoimmune process with an unknown initial trigger. There is no cure, but many different medications and procedures have been used in efforts to control the symptoms.
Pityriasis rubra pilaris refers to a group of chronic disorders characterized by reddish orange, scaling plaques and keratotic follicular papules. Symptoms may include reddish-orange patches on the skin, severe flaking, uncomfortable itching, thickening of the skin on the feet and hands, and thickened bumps around hair follicles. For some, early symptoms may also include generalized swelling of the legs, feet and other parts of the body. PRP has a varied clinical progression and a varied rate of improvement. There is currently no known cause or cure for PRP.
Granuloma annulare (GA) is a rare, sometimes chronic skin condition which presents as reddish bumps on the skin arranged in a circle or ring. It can initially occur at any age, though two-thirds of patients are under 30 years old, and it is seen most often in children and young adults. Females are two times as likely to have it as males.
Eosinophilic folliculitis is an itchy rash with an unknown cause that is most common among individuals with HIV, though it can occur in HIV-negative individuals where it is known by the eponym Ofuji disease. EF consists of itchy red bumps (papules) centered on hair follicles and typically found on the upper body, sparing the abdomen and legs. The name eosinophilic folliculitis refers to the predominant immune cells associated with the disease (eosinophils) and the involvement of the hair follicles.
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".
Actinic prurigo is a rare sunlight-induced, pruritic, papular, or nodular skin eruption. Some medical experts use the term actinic prurigo to denote a rare photodermatosis that develops in childhood and is chronic and persistent; this rare photodermatosis, associated with the human leukocyte antigen HLA-DR4, is often called "Familial polymorphous light eruption of American Indians" or "Hereditary polymorphous light eruption of American Indians" but some experts consider it to be a variant of the syndrome known as polymorphous light eruption (PMLE). Some experts use the term actinic prurigo for Hutchinson's summer prurigo and several other photodermatoses that might, or might not, be distinct clinical entities.
Alopecia mucinosa, also known as Follicular mucinosis, Mucinosis follicularis, Pinkus' follicular mucinosis, and Pinkus' follicular mucinosis–benign primary form, is a skin disorder that generally presents, but not exclusively, as erythematous plaques or flat patches without hair primarily on the scalp, neck and face. This can also be present on the body as a follicular mucinosis and may represent a systemic disease.
Lichen myxedematosus is a group of cutaneous disorders considered mucinoses. Conditions included in this group are:
Discrete papular lichen myxedematosus is a skin condition caused by fibroblasts producing abnormally large amounts of mucopolysaccharides characterized by the occurrence of waxy, flesh-colored papules..
Acral persistent papular mucinosis (APPM) is a rare form of lichen myxedematosus. It is characterized by small papules on the backs of the hands, wrists, and extensor aspects of the distal forearms, with no further clinical or laboratory indications. Lesions tend to persist and may grow in number gradually. Because there are no symptoms, treatment is rarely required.
Self-healing papular mucinosis is a skin condition caused by fibroblasts producing abnormally large amounts of mucopolysaccharides, and may present in adult and juvenile forms. The juvenile variant is also called self-healing juvenile cutaneous mucinosis.
Papular mucinosis of infancy is a skin condition caused by fibroblasts producing abnormally large amounts of mucopolysaccharides, characterized by skin-colored or translucent papules.
Majocchi's granuloma is a skin condition characterized by deep, pustular plaques, and is a form of tinea corporis. It is a localized form of fungal folliculitis. Lesions often have a pink and scaly central component with pustules or folliculocentric papules at the periphery. The name comes from Domenico Majocchi, who discovered the disorder in 1883. Majocchi was a professor of dermatology at the University of Parma and later the University of Bologna. This disease is most commonly caused by filamentous fungi in the genus Trichophyton.
Generalized granuloma annulare is a skin condition of unknown cause, tending to affect women in the fifth and sixth decades, presenting as a diffuse but symmetrical, papular or annular eruption of more than ten skin lesions, and often hundreds.
Cutaneous lymphoid hyperplasia refers to a groups of benign cutaneous disorders characterized by collections of lymphocytes, macrophages, and dendritic cells in the skin. Conditions included in this groups are:
Atypical tuberous myxedema, also known as Jadassohn–Dosseker syndrome, is thought to represent a pure nodular variant of lichen myxedematosus.
Nodular lichen myxedematosus is a cutaneous condition characterized by multiple nodules on the limbs and trunk, with a mild or absent papular component.
Cutaneous lupus mucinosis, also known as papular and nodular mucinosis in lupus erythematosus, papular and nodular mucinosis of Gold, and papulonodular mucinosis in lupus erythematosus, is a cutaneous condition characterized by lesions that present as asymptomatic skin-colored, at times reddish, 0.5–2 cm papules and nodules.
Palpable purpura is characterized by firm, elevated hemorrhagic plaques or papules that can measure several centimeters in diameter. These are typically found on dependent surfaces, like the back of a recumbent patient or the lower legs. The center of a lesion may become ulcerative, pustular, vesicular, necrotic, or nodular. They tend to be asymptomatic, but when nodular or ulcerative, they can become tender. Palpable purpura is the most common cutaneous lesion among individuals with inflammatory vascular injury, whereas nonpalpable purpura typically indicates bleeding caused by a platelet or coagulation disorder.
