Dental Problems

Lichen Planus

TeethEramus Wilson described Lichen planus in 1869. It may involve various mucosal surfaces either concurrectly or independently, with serially or cutaneous involvement. Oral mucosa is frequently involved. It is a probable precancerous conditions. Lichen planus is a common inflammatory disease of the skin presenting with characteristic violaceous, pruritic papules, polygonal. This disease may also affect the nails, hair and mucosa. In this article, there is a brief discussion on the lichen planus disease -definition, types, etiology and syndromes associated with lichen planus.

Definition:

Lichen planus is a relatively common dermatological disorder occurring on the oral mucus membrane and skin. It refers to the lace-like pattern produced by symbolic fungal and algae colonies on the surface of rocks in nature (lichens).

Types:

The following are the various types of lichen planus:

  • Reticular
  • Papular
  • Plaque
  • Atropic
  • Classical
  • Erythematous
  • Ulcerative
  • Hypertrophic
  • Erosive
  • Bullous
  • Hypertrophied
  • Annular
  • Actinic
  • Follicular
  • Linear

Immunology:

i. Cell mediated immune response:

  • It is a cell mediated immune response associated with lymphocyte-epidermal interactions, resulting in degeneration of basal cell layer. Possible hypothesis are as follows.
    • Alternation of keratinocytes as a result of unknown events resulting in antigenic alternation of these cells thereby stimulating immunological reaction.
    • A primary immunologic reaction causing alternation and degeneration of keratinocytes.
  • Cell mediated immune response may be caused by various mononuclear cells, i.e. langerhan’s cells, macrophages predominantly T lymphocytes, lymphoblast cells, B lymphocytes and mast cells. These cells infiltrate the upper part of lamina propria of sub mucosa.
  • In this cell mediated response Langerhan’s cells are potent antigen presenting cells, lymphocytes are effective cells and keratinocytes are target cells.
  • The macrophages are mostly mature, which probably have functional role with mononuclear cells is suggesting of cell to cell cooperation.
  • Recent hypothesis of pathogenesis of lichen planus. In a genetically predisposed individual haptens (certain drug or dental material), conventional antigen or super-antigen of oral microbial origin can induce cell mediated immune response resulting in subepthelial T-cell infiltration of the site in oral mucosa with cytokine generation HSP-60 and C 1/10 expression by basal keratinocytes. If individual is not predisposed to react to HSp-60, then non-specific mucositis occur. If the individual has genetic predisposition, it results in autoimmune reaction , then activation of cytotoxic T cell, later destruction of basal keratinocytes and oral lichen planus.

ii. Autoimmunity:

  • The activated T lymphocytes also secrete gamma interferons which induce keratinocytes to produce HLA-DR and increase their rate of differentiation with the formation of thickened surface.
  • Antigenic information is transderred from langerhans cells to lymphocytes, when there is mutual expression of HLA-DR. Lympocytes normally are attracted towards HLA-DR expressing kertinocytes and may contact the epithelial cell.
  • During this contact, inappropriate epithelial antigenic information ma be passed to lymphocytes due to HLA-DR linkage. With this mechanis, self antigen may be recognized as foreign bodies, leading to destruction of basal cells, resulting in an auto-immune response.
  • Autoimmune disorders classically have female predilection and are associated with serum antibodies with hypergamma-globulinemia.
  • There are numerous studies which show immune depsits in lichen planus affected tissues but it is not specific.

iii. Immunodeficiency:

There has been report of decreased serum levels of IgG, IgA or IgM in lichen planus and the possibility of it, as a manifestation of immunodeficiency has been raised. But at the same times, reports of normal concentrations of IgA and IgM are found: therefore the role of immunodeficiency is questionable.

Genetic factors:

  • Cases of lichen planus are reported in families, twins and wife and husband.
  • Clinically, familial lichen planus is somewhat unusual as it appears to affect young patients, is sever, often extensive, involves skin, nails and mucous membrane and is persistent.
  • It has also been suggested that familial cause might be environmental and related to infection, rather than no genetics.

Infections

A bacterial etiology may be there but results are not confirmed. Spirochetes and rod-like bodies resembling bacteria have also been detected.

Drugs and chemicals:

  • It is also called as lichenoid reaction. Although, the clinical disease of lichen planus has an immunological basis, some persons with lichen planus have a diathesis for the disorder.
  • Te tissues of a person with diathesis react in a special way to certain extrinsic stimuli, making it more susceptible to certain diseases.
  • Drugs act to increase temporarily the specific antigenic stimulus and hence increase the reaction. If the drug is withdrawn at a later time, the antigenic stimulus is reduced, followed by reduction in clinical severity.
  • It is suggested that drugs that are known to induce lichenoid response, act as agents which amplify the disorder, rather than induce it.
  • To implicate a drug responsible for a lichenoid reaction can be difficult as there is no specific test for it.
  • Association between dental filling material and lichen planus has also been suggested.

Psychogenic factor:

  • A relationship of lichen planus with stress is quoted and neurogenic basis is suggested.
  • Observation mostly in nervous and highly stressed persons is associated with emotional upset, over work and some form of mental strain.

Habit:

  • Oral lichen planus have shown associated with tobacco habit. Chewers of tobacco and betel have increased prevalence of oral lichen planus.
  • Smoking may play a role in initiating oral lichen planus of plaque type.

Miscellaneous:

  • Occurrence of lichen planus is also suggested in associated with deficiency of vitamin B1, B6 and C, electric potential difference, anemia and patients with secondary syphilis.
  • It can also occur in some cases due to trauma and malnutrition.
  • Exacerbation of lichen planus also correspond to periods of emotional upset, overwork, anxiety, hysteria attack, depression and some form of mental strain.

Syndromes associated with lichen planus

  • Grinspan syndrome
    • Lichen palnus
    • Dibetes mellitus
    • Vascular hypertension
  • Graham little syndrome

The above article discusses about lichen planus.

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