Etiology
Although the etiology of lichen sclerosus (LS) is unknown, autoimmune, genetic, and hormonal factors have been implicated. Trauma and infection are also thought to play a role as potential triggers of disease.
Studies estimate that between 8% and 12% of patients have a first-degree relative with LS, suggestive of a potential familial link.[19][20]
Studies have suggested a T helper 1 (TH1)-mediated immune response and have found alterations in microRNAs, specifically miR-155, as well as galectin-7, which regulates collagen I and III changes.[21][22] LS has been associated with various autoimmune conditions and most commonly with autoimmune thyroid disorders.[23] A large case-control study of 765 women with LS found a statistically significant association of autoimmune conditions including autoimmune thyroiditis (odds ratio [OR] 2.67, P <0.001), hypothyroidism (OR 2.34, P <0.001), and hyperthyroidism (OR 2.05, P <0.001) compared with matched controls.[24] Autoimmune disorders may be more commonly found in women with LS in comparison with men with the condition.[25] One study of 532 patients found that lichen sclerosus was significantly more often associated with at least one autoimmune disease in women compared with men (OR 4.3, 95% CI 1.9 to 9.6).[25]
Obesity and metabolic syndrome are more common in patients with LS.[15][26][27] One cross-sectional study found that adult patients with LS were more frequently overweight or obese (age-standardized prevalence ratio 1.44, 95% CI 1.30 to 1.59).[15]
Although several infective agents have been associated with LS, including bacterial triggers such as borrelia and viral triggers such as human papillomavirus, the evidence is currently conflicting.[28]
Local causes such as injury or trauma to skin may be a precipitating factor for the condition; LS is known to first appear in sites of trauma such as in operative scars (Koebnerization).
Although the condition may affect people of all ages, there is increased incidence in postmenopausal women. One cross-sectional study of 729 patients with LS found that mean age at symptom onset was 51.4 +/- 18.1 years.[15]
Pathophysiology
LS is a T-cell mediated inflammatory disorder affecting the skin and mucosa, with a predilection for the vulvar and perianal area.[29] Over time, inflammation results in atrophic and sclerotic changes to the epidermis if left untreated.
Infiltration of cytotoxic T lymphocytes into the dermis and altered fibroblast function play a role in disease processes, with T lymphocytes considered an earlier histologic finding, and fibroblasts changes and resultant fibrosis and vascular damage seen in later stages. Hypoxia and vascular damage are evident in affected skin, but the inciting events characterizing this and the exact mechanisms are unknown. ECM-1 autoantibody has been implicated and is thought to affect matrix metalloproteinases, which are in turn thought to affect transforming growth factor-beta (TGF-beta) with changes in collagen deposition.[30]
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