Pityriasis lichenoides chronica: From clinical polymorphism to diagnostic verification. Case report

Abstract

Pityriasis lichenoides chronica (PLC) is a chronic inflammatory dermatosis of unknown etiology, primarily affecting individuals in their youth and middle age. The clinical polymorphism associated with the rash often complicates the differential diagnosis with other papulosquamous diseases, resulting in diagnostic errors. This case study underscores the importance of a comprehensive clinical and instrumental approach to accurately verify this condition, using our clinical observation as a basis. A 28-year-old male presented to a dermatologist with a generalized itchy rash. At the prehospital stage, the patient was misdiagnosed with allergic dermatitis, guttate psoriasis, and lichen planus due to the similar symptoms, and previous treatments proved ineffective. Upon detailed examination, a symmetrical rash characterized by multiple papules, with wafer-like scales and hemorrhagic elements, was identified on the lower extremities. Dermatoscopy played a crucial role in rectifying the diagnosis, revealing monomorphic punctate vessels and peripheral hypopigmentation. Additionally, a histological examination of a skin biopsy confirmed the diagnosis of PLC by demonstrating parakeratosis, focal spongiosis, keratinocyte apoptosis, basal layer vacuolation, and erythrocyte extravasation. A combination therapy was initiated to address persistent symptoms, including narrow-band ultraviolet B (311 nm) phototherapy, systemic methotrexate at 15 mg per week, and the topical glucocorticosteroid clobetasol. Treatment was well tolerated, with no significant adverse effects. This approach resulted in substantial clinical improvement, complete regression of the rash, and sustained remission over a 4-month follow-up. Therefore, it is imperative to include PLC into the differential diagnostic algorithm for any chronic papulosquamous dermatoses. Early implementation of skin biopsy and dermatoscopy provides reliable diagnostic direction, and the combination of phototherapy and systemic immunosuppression with methotrexate represents a highly effective strategy for managing resistant forms of the disease. This approach minimizes the risk of chronicity and significantly improves patients' quality of life.