D3.233 - Polypharmacy-Associated Lichenoid Eruption Simulating Keratosis Lichenoides Chronica

1.⁠ ⁠Background

Lichenoid drug eruptions (LDE) are delayed-type hypersensitivity reactions that can clinically and histopathologically mimic various lichenoid dermatoses. Keratosis lichenoides chronica (KLC) is an extremely rare, treatment-resistant mucocutaneous disorder characterized by linear or reticulated lichenoid papules. This case highlights the importance of considering drug-induced etiologies in patients presenting with clinical features suggestive of KLC, emphasizing the role of polypharmacy management. 

2.⁠ ⁠Case Description

A 72-year-old female presented to the dermatology department with a 2-year history of generalized, severely pruritic, erythematous papular lesions. She had concomitant type 2 diabetes, hypertension, MGUS, and nephrotic syndrome. 

Due to the characteristic linear arrangement and chronic nature of the lesions, the dermatology clinic performed a punch biopsy with a preliminary diagnosis of Keratosis Lichenoides Chronica (KLC). The histopathology report supported this suspicion, showing interface dermatitis with basal vacuolar degeneration, though a prominent eosinophilic infiltrate was also noted. Despite long-term use of high-dose antihistamines and various systemic/topical corticosteroids prescribed by dermatology, the symptoms remained refractory. The patient was subsequently referred to the allergy department for a detailed evaluation of her extensive medication list: ⁠Valsartan/HCTZ,  ⁠Atorvastatin, Empagliflozin, Insulin, Aspirin

3.⁠ ⁠Results

Considering the histological finding of tissue eosinophilia and the patient's lack of response to standard treatments for Keratosis Lichenoides Chronica (KLC), a drug-induced lichenoid reaction was suspected. Consequently, the administration of Valsartan/Hydrochlorothiazide, Atorvastatin, and Empagliflozin was discontinued in consultation with the patient's primary care physicians. To maintain disease control, antihypertensive therapy was switched to Amlodipine, and insulin dosages were titrated accordingly. Following this drug de-challenge, the patient reported complete cessation of pruritus within a few weeks. Subsequent follow-up examinations revealed full resolution of the KLC-like cutaneous lesions, obviating the need for further corticosteroid therapy

4.⁠ ⁠Conclusion

This case demonstrates that LDE can perfectly mimic rare dermatological conditions like KLC, even when the clinical suspicion is strong enough to lead to a biopsy for KLC. In elderly patients with polypharmacy, a high index of suspicion for drug-induced reactions is crucial. Identifying the culprit drug can prevent misdiagnosis and the unnecessary use of long-term, high-dose immunosuppressive treatments.