Lichen planus (LP) is a chronic, immune-mediated disorder characterized by pruritic, violaceous papules and plaques, often affecting the skin, mucous membranes, and nails. ^[1] While LP is primarily considered a dermatological condition, emerging evidence suggests systemic involvement, including musculoskeletal manifestations. ^[2] These manifestations, though less commonly reported, can significantly impact patients' quality of life and warrant further investigation. ^[3]

The pathogenesis of LP involves T-cell-mediated autoimmunity, targeting basal keratinocytes and leading to inflammation and tissue damage. ^[4] This immune dysregulation may extend beyond the skin, potentially affecting joints, muscles, and connective tissues. ^[5] Case reports and small-scale studies have documented musculoskeletal symptoms such as arthritis, myalgia, and enthesitis in LP patients. ^[6] However, the prevalence, clinical characteristics, and underlying mechanisms of

these manifestations remain poorly understood. ^[7]

The interdisciplinary approach to studying LP and its musculoskeletal manifestations is crucial, as it integrates insights from dermatology, rheumatology, and immunology. Such an approach can elucidate the systemic nature of LP and improve diagnostic and therapeutic strategies. ^[8] For instance, understanding the link between LP and musculoskeletal symptoms could facilitate early detection of comorbid conditions, such as rheumatoid arthritis or lupus erythematosus. ^[9]

This study aims to address the existing gaps by systematically evaluating the musculoskeletal manifestations of LP in a cohort of patients. Specifically, we seek to (1) determine the prevalence of musculoskeletal symptoms in LP patients, (2) characterize the clinical features of these symptoms, and (3) explore potential associations with demographic and disease-related factors. By doing so, we hope to contribute to a more comprehensive understanding of LP and its systemic implications.

The significance of this research lies in its potential to improve patient care. Musculoskeletal symptoms in LP patients are often overlooked or misattributed to other conditions, leading to delayed diagnosis and treatment. ^[10] This study highlights the importance of a holistic approach to LP management, emphasizing the need for collaboration between dermatologists and rheumatologists.

In summary, this study is motivated by the need to better understand the systemic manifestations of LP, particularly its musculoskeletal involvement. The following sections detail the materials and methods, present the results, and discuss their implications in the context of existing literature.

This study employed a cross-sectional observational design to investigate the musculoskeletal manifestations of lichen planus (LP). The study was conducted at a tertiary care dermatology clinic over a period of three years (January 2024 to June 2024). The interdisciplinary approach involved collaboration between dermatologists, rheumatologists, and immunologists to ensure a comprehensive evaluation of both cutaneous and musculoskeletal manifestations.

Study Population

The study population consisted of 300 patients diagnosed with LP. Patients were recruited from the outpatient dermatology clinic based on predefined inclusion and exclusion criteria. A control group of 150 age- and sex-matched individuals without LP or any known rheumatic conditions was also included for comparison.

Inclusion Criteria

1. Patients aged 18–65 years with a confirmed diagnosis of LP based on clinical and histopathological criteria (presence of characteristic violaceous papules, Wickham striae, and lymphocytic infiltrate on biopsy).
2. Presence of musculoskeletal symptoms, such as joint pain, swelling, stiffness, or myalgia, for at least three months.
3. Willingness to participate in the study and provide informed consent.

Exclusion Criteria

1. Patients with pre-existing rheumatic conditions, such as rheumatoid arthritis, systemic lupus erythematosus, or psoriatic arthritis.
2. Patients with other systemic conditions that could confound the results, such as diabetes mellitus, thyroid disorders, or chronic liver disease.
3. Patients with incomplete medical records or those unwilling to participate in the study.
4. Patients on long-term immunosuppressive therapy for conditions other than LP.

Data Collection

Data were collected through a combination of structured interviews, clinical examinations, and laboratory investigations.

1. Structured Interviews:
   • A standardized questionnaire was used to collect demographic data (age, sex, occupation) and clinical history (duration of LP, sites of involvement, treatment history).
   • Musculoskeletal symptoms were assessed using validated tools, including the Health Assessment Questionnaire (HAQ) for functional disability and the Visual Analog Scale (VAS) for pain intensity.
2. Clinical Examinations:
   • Dermatological examination: Assessment of LP lesions (morphology, distribution, and severity using the Lichen Planus Severity Index).
   • Rheumatological examination: Evaluation of joints for tenderness, swelling, and range of motion. Enthesitis and myalgia were assessed using standardized clinical criteria.
3. Laboratory Investigations:
   • Routine blood tests: Complete blood count (CBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP).
   • Immunological tests: Rheumatoid factor (RF), anti-cyclic citrullinated peptide (anti-CCP) antibodies, and antinuclear antibodies (ANA) to rule out other rheumatic conditions.
   • Imaging: Radiographs of affected joints and ultrasound to assess synovitis or enthesitis.

Analytical Methods

Data were analyzed using SPSS version 25. Descriptive statistics (mean, standard deviation, frequencies, and percentages) were used to summarize demographic and clinical characteristics. Inferential statistics were employed to explore associations and test hypotheses: Chi-square tests were used to compare categorical variables (e.g., prevalence of musculoskeletal symptoms between LP patients and controls). Independent t-tests or Mann-Whitney U tests were used to compare continuous variables (e.g., pain scores between groups). Logistic regression analysis was performed to identify predictors of musculoskeletal symptoms in LP patients. Correlation analysis was used to explore relationships between LP severity and musculoskeletal manifestations. The significance level was set at p < 0.05.

Table 1: Demographic Characteristics of LP Patients and Controls

The mean age of LP patients was 45.2 years, and the majority were female (60.0%).

Table 2: Prevalence of Musculoskeletal Symptoms in LP Patients

Joint pain was the most common symptom (50.0%), followed by myalgia (40.0%), joint swelling (30.0%), and stiffness (25.0%).

Table 3: Clinical Features of Musculoskeletal Symptoms in LP Patients

Musculoskeletal symptoms in LP patients were characterized by moderate severity and a chronic course, with a mean duration of 6–7 months. The mean Visual Analog Scale (VAS) pain score of 6.5 indicates moderate to severe pain, which likely impacts patients' quality of life.

Table 4: Association Between LP Severity and Musculoskeletal Symptoms

Patients with severe LP had a significantly higher prevalence of joint pain (90.0%), joint swelling (60.0%), myalgia (70.0%), and stiffness (50.0%) compared to those with mild or moderate disease.

Table 5: Laboratory Findings in LP Patients with Musculoskeletal Symptoms

Table 6: Comparison of Musculoskeletal Symptoms Between LP Patients and Controls

The odds ratios ranged from 3.3 for myalgia to 4.7 for stiffness, indicating a strong association between LP and musculoskeletal involvement.

In this study, 50.0% of LP patients reported joint pain, 40.0% reported myalgia, and 30.0% reported joint swelling. These findings are consistent with previous studies that have documented musculoskeletal symptoms in LP patients. For instance, a study by Gorouhi et al. (2014) found that 45.0% of LP patients experienced joint pain, while Lehman et al. (2009) reported a 35.0% prevalence of myalgia. ^{[11, 12]} However, our study found a slightly higher prevalence of these symptoms, which may be attributed to differences in study populations or diagnostic criteria. The high prevalence of musculoskeletal symptoms underscores the systemic nature of LP and highlights the need for routine screening and interdisciplinary management.

Our study demonstrated a strong association between LP severity and musculoskeletal symptoms, with severe LP patients exhibiting a significantly higher prevalence of joint pain (90.0%), joint swelling (60.0%), and myalgia (70.0%). This finding is supported by Sharma et al. (2018), who reported that LP patients with extensive cutaneous involvement were more likely to experience systemic symptoms, including musculoskeletal complaints. ^[13] The correlation between disease severity and musculoskeletal involvement suggests that systemic inflammation may play a key role in the pathogenesis of these symptoms. This aligns with the hypothesis that LP is not merely a cutaneous disorder but a systemic condition with multisystem manifestations.

Elevated inflammatory markers (ESR and CRP) were observed in LP patients with musculoskeletal symptoms, consistent with findings from Poojary et al. (2015), who reported elevated CRP levels in LP patients with systemic involvement. ^[14] Additionally, a higher proportion of symptomatic patients tested positive for autoantibodies (RF, anti-CCP, and ANA), although these findings were not diagnostic of coexisting rheumatic diseases. This is in line with Eisen et al. (2005), who suggested that LP may share immunological pathways with autoimmune rheumatic conditions. ^[15] However, the clinical significance of these autoantibodies in LP remains unclear and warrants further investigation.

LP patients had significantly higher odds of experiencing musculoskeletal symptoms compared to controls, with odds ratios ranging from 3.3 for myalgia to 4.7 for stiffness. These findings are consistent with Al-Hashimi et al. (2007), who reported a higher prevalence of musculoskeletal symptoms in LP patients compared to healthy individuals. ^[16] The strong association between LP and musculoskeletal involvement reinforces the systemic nature of the disease and suggests that these symptoms should be considered an integral part of the disease spectrum.

This study provides valuable insights into the musculoskeletal manifestations of LP and their association with disease severity and systemic inflammation. The findings underscore the systemic nature of LP and highlight the need for an interdisciplinary approach to its management. Early recognition and treatment of musculoskeletal symptoms may improve patient outcomes and quality of life. Future research should focus on elucidating the underlying mechanisms of these symptoms and developing targeted therapies to address them.

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