Comorbidity in Lichen Planus: A Retrospective Population-Based Case-Control Study in Sweden

Area of Science:

• Dermatology
• Immunology
• Epidemiology

Background:

• Lichen planus (LP) is a chronic, immune-mediated inflammatory condition affecting skin and mucous membranes.
• Etiology remains largely unknown, and associations with comorbidities require further investigation, especially in specific populations.
• Limited data exists on LP prevalence, incidence, and comorbidities within Swedish populations.

Purpose of the Study:

• To determine the prevalence and incidence of Lichen planus (LP) in a Swedish population.
• To assess the diagnostic validity of ICD-10 coding for LP (L43).
• To identify comorbidities associated with LP and evaluate treatment patterns.

Main Methods:

• Retrospective, population-based case-control study of 361,812 individuals in Region Jönköping, Sweden (2013-2022).
• Calculated incidence and prevalence rates.
• Assessed diagnostic validity via medical record review of 70 cases to determine positive predictive value (PPV); analyzed comorbidity associations using logistic regression.

Main Results:

• Calculated prevalence of 235.5 and incidence of 19.6 per 100,000 inhabitants.
• The PPV of ICD-10 coded LP diagnosis was 78.6%, yielding an adjusted prevalence of 184.9 per 100,000.
• Significant associations found between LP and thyroid, malignant, metabolic, and autoimmune conditions; over one-third of patients received topical corticosteroids.

Conclusions:

• Lichen planus is relatively uncommon in this Swedish population.
• ICD-10 coding for LP demonstrates acceptable diagnostic validity.
• The identified comorbidities underscore the importance of comprehensive patient assessment in managing LP.