Lichen planus (LP) is a chronic inflammatory and immune-mediated disease that affects the skin, nails, hair, and mucous membranes. It is not an actual lichen, and is only named that because it looks like one. 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. 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.
A papule is a circumscribed, solid elevation of skin with no visible fluid, varying in area from a pinhead to 1 cm. Papules can be brown, purple, pink or red in color, and can cluster into a papular rash. They may open when scratched and become infected and crusty. Larger non-blisterform elevated lesions may be termed nodules.
Tuberculosis verrucosa cutis 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.
Lichen ruber moniliformis is a rare skin disease named for Fred Wise and Charles R. Rein.
Pruritic urticarial papules and plaques of pregnancy (PUPPP), known in United Kingdom as polymorphic eruption of pregnancy (PEP), is a chronic hives-like rash that strikes some women during pregnancy. It presents no long-term risk for either the mother or unborn child despite frequently severe pruritus. PUPPP frequently begins on the abdomen and spreads to the legs, feet, arms, chest, and neck.
Lichen spinulosus is a rare skin disorder characterized by follicular keratotic papules that are grouped into large patches. It is a variant of keratosis pilaris named for its resemblance to a patch of lichen.
Fox–Fordyce disease is a chronic blockage of the sweat gland ducts with a secondary, non-bacterial inflammatory response to the secretions and cellular debris in the cysts. The inflammation is often accompanied by intense itching. In general, the disease often causes skin to darken near the affected area and raised bumps or papules to appear. In addition, hair follicles can become damaged which cause hair loss. Hidradenitis is very similar, but tends to have a secondary bacterial infection so that pus-draining sinuses are formed. It is a very devastating skin disease that does not have universally curative treatments.
Papular mucinosis is a rare skin disease. Localized and disseminated cases are called papular mucinosis or lichen myxedematosus while generalized, confluent papular forms with sclerosis are called scleromyxedema. Frequently, all three forms are regarded as papular mucinosis. However, some authors restrict it to only mild cases. Another form, acral persistent papular mucinosis is regarded as a separate entity.
Dermatoses of pregnancy are the inflammatory skin diseases that are specific to women while they are pregnant. While some use the term 'polymorphic eruption of pregnancy' to cover these, this term is a synonym used in the UK for Pruritic urticarial papules and plaques of pregnancy, which is the commonest of these skin conditions.
Grover's disease (GD) is a polymorphic, pruritic, papulovesicular dermatosis characterized histologically by acantholysis with or without dyskeratosis. Once confirmed, most cases of Grover's disease last six to twelve months, which is why it was originally called "transient". However it may last much longer. Nevertheless, it is not to be confused with relapsing linear acantholytic dermatosis.
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".
Primary cutaneous amyloidosis is a form of amyloidosis associated with oncostatin M receptor. This type of amyloidosis has been divided into the following types:
Methotrexate-induced papular eruption appears in patients being treated with methotrexate, such as those with rheumatic disease, presenting with erythematous indurated papules, usually located on the proximal extremities.
Lichen striatus 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.
Papulonecrotic tuberculid is usually an asymptomatic, chronic skin disorder, presenting in successive crops, skin lesions symmetrically distributed on the extensor extremities.
Lichen aureus is a skin condition characterized by the sudden appearance of one or several golden or rust-colored, closely packed macules or lichenoid papules.
Papular eruption of blacks is a cutaneous condition characterized clinically by small, pruritic papules and histologically by a mononuclear cell-eosinophil perivascular infiltrate.
A syphilid is any of the cutaneous and mucous membrane lesions characteristic of secondary and tertiary syphilis.
Sarcoidosis, an inflammatory disease, involves the skin in about 25% of patients. The most common lesions are erythema nodosum, plaques, maculopapular eruptions, subcutaneous nodules, and lupus pernio. Treatment is not required, since the lesions usually resolve spontaneously in two to four weeks. Although it may be disfiguring, cutaneous sarcoidosis rarely causes major problems.
