The risk for development of non-melanoma skin cancers is also increased. Psoriasis increases the risk of developing squamous cell carcinoma of the skin by 431% and increases the risk of basal cell carcinoma by 100%. There is no increased risk of melanoma associated with psoriasis. People with psoriasis have a higher risk of developing cancer. Epidemiology
Psoriasis is estimated to affect 2–4% of the population of the western world. The rate of psoriasis varies according to age, region and ethnicity; a combination of environmental and genetic factors is thought to be responsible for these differences. It can occur at any age, although it most commonly appears for the first time between the ages of 15 and 25 years. Approximately one third of people with psoriasis report being diagnosed before age 20. Psoriasis affects both sexes equally.Psoriasis affects about 6.7 million Americans and occurs more frequently in adults.Psoriasis is about five times more common in people of European descent than in people of Asian descent.People with inflammatory bowel disease such as Crohn disease or ulcerative colitis are at an increased risk of developing psoriasis. Psoriasis is more common in countries farther from the equator. Persons of white European ancestry are more likely to have psoriasis and the condition is relatively uncommon in African Americans and extremely uncommon in Native Americans. History
Scholars believe psoriasis to have been included among the various skin conditions called tzaraath (translated as leprosy) in the Hebrew Bible, a condition imposed as a punishment for slander.
Annular lichen planus 
Atrophic lichen planus
Bullous lichen planus (vesiculobullous lichen planus)
Erosive lichen planus
Erythema dyschromicum perstans (ashy dermatosis, dermatosis cinecienta)
Giant cell lichenoid dermatitis
Hepatitis-associated lichen planus
Hypertrophic lichen planus (lichen planus verrucosus)
Idiopathic eruptive macular pigmentation
Inverse lichen planus
Keratosis lichenoides chronica (Nékams disease)
Kraurosis vulvae
Lichen nitidus
Lichen planus actinicus (actinic lichen niditus, actinic lichen planus, lichen planus atrophicus annularis, lichen planus subtropicus, lichen planus tropicus, lichenoid melanodermatitis, lichenoid melanodermatosis, summertime actinic lichenoid eruption)
Lichen planus pemphigoides
Lichen planus pigmentosus
Lichen planus–lichen sclerosus overlap syndrome
Lichen ruber moniliformis
Lichen sclerosus (lichen sclerosus et atrophicus)
Lichen striatus (Blaschko linear acquired inflammatory skin eruption, linear lichenoid dermatosis)
Lichen verrucosus et reticularis
Lichenoid trikeratosis
Lichenoid dermatitis
Lichenoid reaction of graft-versus-host disease
Linear lichen planus
Mucosal lichen planus
Peno-gingival syndrome
Ulcerative lichen planus
Vulvovaginal gingival syndrome
Vulvovaginal lichen planus

Lymphoid-related
Lymphoid-related cutaneous conditions are a group of disorders characterized by collections of lymphocyte cells within the skin.