Possible Mechanisms Involved in the Cooccurrence of Oral Lichen Planus and Hashimoto's Thyroiditis

Oral and non-oral lichen planus show genetic heterogeneity and differential risk for autoimmune disease and oral cancer

Lichen planus (LP) is a T-cell-mediated inflammatory disease affecting squamous epithelia in many parts of the body, most often the skin and oral mucosa. Cutaneous LP is usually transient and oral LP (OLP) is most often chronic, so we performed a large-scale genetic and epidemiological study of LP to address whether the oral and non-oral subgroups have shared or distinct underlying pathologies and their overlap with autoimmune disease. Using lifelong records covering diagnoses, procedures, and clinic identity from 473,580 individuals in the FinnGen study, genome-wide association analyses were conducted on carefully constructed subcategories of OLP (n = 3,323) and non-oral LP (n = 4,356) and on the combined group. We identified 15 genome-wide significant associations in FinnGen and an additional 12 when meta-analyzed with UKBB (27 independent associations at 25 distinct genomic locations), most of which are shared between oral and non-oral LP. Many associations coincide with known autoimmune disease loci, consistent with the epidemiologic enrichment of LP with hypothyroidism and other autoimmune diseases. Notably, a third of the FinnGen associations demonstrate significant differences between OLP and non-OLP. We also observed a 13.6-fold risk for tongue cancer and an elevated risk for other oral cancers in OLP, in agreement with earlier reports that connect LP with higher cancer incidence. In addition to a large-scale dissection of LP genetics and comorbidities, our study demonstrates the use of comprehensive, multidimensional health registry data to address outstanding clinical questions and reveal underlying biological mechanisms in common but understudied diseases.

Crossroads between Skin and Endocrine Glands: The Interplay of Lichen Planus with Thyroid Anomalies

In this narrative review, we aimed to overview the interplay between lichen planus (LP) and thyroid conditions (TCs) from a dual perspective (dermatologic and endocrine), since a current gap in understanding LP-TC connections is found so far and the topic is still a matter of debate. We searched PubMed from Inception to October 2023 by using the key terms "lichen planus" and "thyroid", (alternatively, "endocrine" or "hormone"). We included original clinical studies in humans according to three sections: LP and TC in terms of dysfunction, autoimmunity, and neoplasia. Six studies confirmed an association between the thyroid dysfunction (exclusively hypothyroidism) and LP/OL (oral LP); of note, only one study addressed cutaneous LP. The sample size of LP/OLP groups varied from 12-14 to 1500 individuals. Hypothyroidism prevalence in OLP was of 30-50%. A higher rate of levothyroxine replacement was identified among OLP patients, at 10% versus 2.5% in controls. The highest OR (odd ratio) of treated hypothyroidism amid OLP was of 2.99 (p < 0.005). Hypothyroidism was confirmed to be associated with a milder OLP phenotype in two studies. A single cohort revealed a similar prevalence of hypothyroidism in LP versus non-LP. Non-confirmatory studies (only on OLP, not cutaneous LP) included five cohorts: a similar prevalence of hypothyroidism among OLP versus controls, and a single cohort showed that the subjects with OLP actually had a lower prevalence of hypothyroidism versus controls (1% versus 4%). Positive autoimmunity in LP/OLP was confirmed in eight studies; the size of the cohorts varied, for instance, with 619 persons with LP and with 76, 92, 105, 108, 192, 247, and 585 patients (a total of 1405) with OLP, respectively; notably, the largest control group was of 10,441 individuals. Four clusters of approaches with respect to the autoimmunity in LP/OLP were found: an analysis of HT/ATD (Hashimoto's thyroiditis/autoimmune thyroid diseases) prevalence; considerations over the specific antibody levels; sex-related features since females are more prone to autoimmunity; and associations (if any) with the clinical aspects of LP/OLP. HT prevalence in OLP versus controls was statistically significantly higher, as follows: 19% versus 5%; 12% versus 6%; and 20% versus 9.8%. A single study addressing LP found a 12% rate of ATDs. One study did not confirm a correlation between OLP-associated clinical elements (and OLP severity) and antibody values against the thyroid, and another showed that positive TPOAb (anti-thyroperoxidase antibodies) was more often found in erosive than non-erosive OLP (68% versus 33%). Just the reverse, one cohort found that OLP subjects had a statistically significantly lower rate of positive TPOAb versus controls (9% versus 15%). Five case-control studies addressed the issue of levothyroxine replacement for prior hypothyroidism in patients that were diagnosed with OLP (no study on LP was identified); three of them confirmed a higher rate of this treatment in OLP (at 8.9%, 9.7%, and 10.6%) versus controls. In conclusion, with regard to LP/OLP-TC, we note several main aspects as practical points for multidisciplinary practitioners: OLP rather than LP requires thyroid awareness; when it comes to the type of thyroid dysfunction, mostly, hypothyroidism should be expected; female patients are more prone to be associated with ATDs; a potential higher ratio of OLP subjects taking levothyroxine was found, thus a good collaboration with an endocrinology team is mandatory; and so far, OLP individuals have not been confirmed to be associated with a higher risk of thyroid nodules/cancer.

CD8 + T-cell marker genes reveal different immune subtypes of oral lichen planus by integrating single-cell RNA-seq and bulk RNA-sequencing

BACKGROUND

Oral lichen planus (OLP) is a local autoimmune disease induced by T-cell dysfunction that frequently affects middle-aged or elderly people, with a higher prevalence in women. CD8 + T cells, also known as killer T cells, play an important role in the progression and persistence of OLP. In order to identify different OLP subtypes associated with CD8 + T cell pathogenesis, consensus clustering was used.

METHODS

In this study, we preprocessed and downscaled the OLP single-cell dataset GSE211630 cohort downloaded from Gene Expression Omnibus (GEO) to finally obtain the marker genes of CD8 + T cells. Based on the expression of marker genes, we classified OLP patients into CMGs subtypes using unsupervised clustering analysis. The gene expression profiles were analyzed by WGCNA using the "WGCNA" R package based on the clinical disease traits and typing results, and 108 CD8 + T-cell related OLP pathogenicity-related genes were obtained from the intersection. Patients were once again classified into gene subtypes based on intersection gene expression using unsupervised clustering analysis.

RESULTS

After obtaining the intersecting genes of CD8 + T cells related to pathogenesis, OLP patients can be precisely classified into two different subtypes based on unsupervised clustering analysis, and subtype B has better immune infiltration results, providing clinicians with a reference for personalized treatment.

CONCLUSIONS

Classification of OLP into different subtypes improve our current understanding of the underlying pathogenesis of OLP and provides new insights for future studies.

Association of Hashimoto’s thyroiditis and anti-thyroid antibodies with oral lichen planus: A cross-sectional study

Hashimoto’s thyroiditis (HT) and its autoantibodies may be associated with oral lichen planus (OLP). In this cross-sectional study, we aimed to assess the relationship among HT, auto-anti-thyroid antibodies, and OLP in a Chinese population of 247 patients with oral lichen planus. Clinical manifestations of OLP were evaluated using the Thongprasom scoring system and clinical type. The diagnosis of HT was based on thyroid function, anti-thyroid peroxidase antibody (anti-TPOAb) and anti-thyroglobulin antibody (anti-TgAb) detection, and ultrasonography. The prevalence of HT in all patients with OLP was 39.68% (98/247); the prevalence in females with OLP was 46.24% (86/186), which was higher than that in males with OLP 19.67% (12/61) (P &lt; 0.01). The titers of the two HT autoantibodies in females with OLP were higher than those in males (P &lt; 0.01). The clinical manifestations of OLP, regardless of being evaluated using the Thongprasom system or clinical type, were not significantly associated with HT development or TPOAb (P = 0.864) or TgAb titers (P = 0.745). In this population-based southern Chinese cohort, the prevalence of HT in patients with OLP, particularly in female patients with OLP, was significantly higher than that in the general population. Female patients had higher HT autoantibody titers than male patients. However, the clinical manifestations of OLP were not significantly correlated with either HT development or auto-anti-thyroid antibody levels. The findings could help further elucidate the factors involved in the relationship between oral lichen planus and Hashimoto’s thyroiditis.

Association between oral health and thyroid disorders: A population-based cross-sectional study

OBJECTIVES

In this study, we aimed to determine the relationship between oral health status and thyroid dysfunction.

METHODS

A population-based cross-sectional analysis using data from the Korean National Health and Nutrition Examination Survey (KNHNES) was performed. We investigated the association between oral health-related parameters and the prevalence of thyroid diseases. In addition, the relationship between oral health status and thyroid function test (TFT) results was analyzed. One-way analysis of variances or chi-square test was used for comparisons between oral health-related parameters and presence of thyroid diseases. Univariable and multivariable logistic regression analyses were conducted to evaluate the associations between participants' characteristics including oral health-related parameters and the abnormal results of TFTs.

RESULTS

A total of 18,034 adults were surveyed. Histories of thyroid diseases were found to be more common in people who brushed their teeth frequently or used oral hygiene products. However, histories of periodontitis and community periodontal index (CPI) did not show significant associations with histories of thyroid diseases. Among 14,860 participants without history of thyroid disorders, people having higher CPI values demonstrated higher probabilities of abnormal TFTs (OR 1.381, 95% CI 1.241-1.537, p < .0001); however, statistical significance was not found after adjusting for the other variables.

CONCLUSIONS

Our study demonstrated that good oral health-related behavior was associated with more frequent thyroid disease history. High CPI showed a significant association with TFT abnormalities; however, the significance of this association became lower when other variables such as age and sex were adjusted. Further studies will be needed to determine how the control of oral health-related conditions actually has a causal relationship with thyroid disease/dysfunction through prospective cohort studies.

Risk factors for frontal fibrosing alopecia: A case-control study in a multiracial population

BACKGROUND

Frontal fibrosing alopecia (FFA) is a chronic cicatricial alopecia with unknown etiology and a worldwide rising incidence.

OBJECTIVE

The objective of this study was to evaluate the association of FFA with demographic and exposure factors in a Brazilian multiracial population.

METHODS

A multicenter case-control study was conducted in 11 referral centers throughout Brazil. The study was a case-control study that prospectively recruited 902 participants (451 patients with FFA and 451 sex-matched control individuals). Study participants completed a thorough questionnaire comprising variables grouped as baseline demographics, environmental exposure, diet, hormonal factors, allergies, and hair and skin care.

RESULTS

When adjusted by sex, age, menopause, and skin color, FFA was associated with hair straightening with formalin (odds ratio [OR], 3.18), use of ordinary (nondermatologic) facial soap (OR, 2.09) and facial moisturizer (OR, 1.99), thyroid disorders (OR, 1.69), and rosacea (OR, 2.08). Smokers (OR, 0.33) and users of antiresidue/clarifying shampoo (OR, 0.35) presented a negative association with FFA. There was no association with the use of sunscreen.

LIMITATIONS

Recall bias.

CONCLUSIONS

The association with moisturizers, ordinary facial soap, and hair straightening with formalin and the negative association with antiresidue/clarifying shampoo reinforce the possibility of an exogenous particle triggering FFA.