Clinicopathological Characteristics of Lichenoid Drug Eruption: A 17-Year Retrospective Study.

Purpose: This study aims to characterize the etiology, clinicopathological features, laboratory findings, management strategies, and clinical outcomes of patients diagnosed with lichenoid drug eruption (LDE). Patients and Methods: A retrospective review was conducted on all biopsy-confirmed LDE cases from January 2008 to October 2024. Data collection included clinical characteristics, causative medications, histopathological as well as laboratory findings, and therapeutic responses. Results: Of the 34 patients, half were male, with a mean age of 65.1 years. LDE most commonly presented as erythematous to violaceous lesions, appearing as patches and plaques, predominantly on the extremities. Histopathology showed lichenoid infiltrates in all cases, with focal infiltration in 58.8%. Parakeratosis was present in 17.7%. Necrotic keratinocytes were found in the basal layer in 82.4% and in the spinous layer in 38.2% of cases. Eosinophilic infiltration was observed in approximately one-third of patients. The most common offending agents were calcium channel blockers (CCBs) (42.5%), followed by statins (25.8%). The median latency period from drug initiation to symptom onset was 10.1 months (interquartile range [IQR] 3.0-45.5). Discontinuation of the causative agent combined with topical corticosteroid therapy resulted in clinical improvement in 73.5% of patients, with a median resolution time of 56 days (IQR 28.0-77.0). Conclusion: Antihypertensive drugs, especially CCBs, were the most frequently implicated triggers of LDE. In addition to lichenoid dermatitis, eosinophilic infiltration served as a key histopathological hallmark of this condition. Timely identification and withdrawal of the causative medication, combined with appropriate treatment, are essential for achieving favorable clinical outcomes.