Lichen planus
Lichen planus is a chronic inflammatory and immune-mediated disease that affects the skin, nails, hair, and mucous membranes. It is characterized by polygonal, flat-topped papules and plaques with overlying, reticulated, fine white scale (Wickham's striae). It is commonly affecting dorsal hands, flexural wrists and forearms, trunk, anterior lower legs and oral mucosa. The cause is unknown, but it is thought to be the result of an autoimmune process with an unknown initial trigger.

To confirm the diagnosis of cutaneous lichen planus, a skin biopsy can be done. Direct immunofluorescence (DIF) can be useful in patients with bullous lesions to differentiate the condition from an autoimmune vesiculobullous disease.

  • Broad lesions on both shins are atypical. In this case, other chronic allergic diseases (lichen simplex chronicus) are usually more suspected.
  • White striations of non-erosive Lichen planus in the buccal mucosa (cheek).
  • It is characterized by the appearance of several itching hard papules. It is a typical appearance of Lichen planus.
  • Leukoplakia ― a white patch in the oral cavity.
  • Atrophic lichen planus
References Cutaneous and mucosal lichen planus: a comprehensive review of clinical subtypes, risk factors, diagnosis, and prognosis 24672362 
Lichen planus (LP) is a chronic inflammatory disorder that most often affects middle-aged adults. LP can involve the skin or mucous membranes including the oral, vulvovaginal, esophageal, laryngeal, and conjunctival mucosa. It has different variants based on the morphology of the lesions and the site of involvement. The literature suggests that certain presentations of the disease such as esophageal or ophthalmological involvement are underdiagnosed. The burden of the disease is higher in some variants including hypertrophic LP and erosive oral LP, which may have a more chronic pattern. LP can significantly affect the quality of life of patients as well. Drugs or contact allergens can cause lichenoid reactions as the main differential diagnosis of LP.
 Lichen Planus 10865927
Lichen planus is a skin condition marked by purplish, flat-topped bumps and patches that can cause intense itching. These skin lesions can be distressing, especially when they affect the mouth or genitals severely. In severe cases, oral lichen planus may even increase the risk of developing a type of skin cancer. It can also affect the scalp and nails. While the cause of most cases is unknown, some may be triggered by certain medications or hepatitis C infection. Treatment typically involves strong creams for localized cases and oral steroids for more widespread ones.
 Oral lichen planus 32753462 
Lichen planus is an immune-mediated inflammatory condition leading to characteristic lesions on skin and mucous membranes. It presents in up to 5% of the general adult population with a female predilection (2:1); the onset is most commonly in middle age. Up to 77% of patients with lichen planus have oral disease, with buccal mucosa the most common subsite. The oral lesions may be asymptomatic, although a subset of patients have pain and difficulty tolerating certain foods (e.g., acidic, spicy) and toothpaste.