Porokeratotic Variant of Lichen Planus

Area of Science:

• Dermatology
• Pathology

Background:

• Lichen planus (LP) is a common inflammatory condition affecting skin and mucous membranes.
• Porokeratosis is a group of disorders characterized by abnormal keratinization.
• The porokerotic variant of LP is a rare subtype with distinct clinical and histopathological features.

Observation:

• A 44-year-old woman presented with a 2-year history of mildly itchy, brownish-black plaques on her face, upper back, and arms.
• Lesions evolved from papules to annular, barely palpable plaques on photo-exposed areas.
• Dermatoscopy revealed characteristic features including a rolled-out, thread, double-marginated border with central atrophy and a brownish reticular background.

Findings:

• Histopathology showed hyperkeratotic epidermis with lymphocytic exocytosis and spongiosis, but the characteristic coronoid lamina of porokeratosis was absent.
• Despite the absence of the coronoid lamina, the combination of clinical morphology, dermatoscopic findings, and pathology supported a diagnosis of porokerotic variant of lichen planus.
• The patient was treated with topical corticosteroids.

Implications:

• This case highlights the importance of integrating clinical, dermatoscopic, and histopathological findings for diagnosing rare dermatological conditions.
• Recognizing the porokerotic variant of lichen planus is crucial for appropriate management and patient counseling.
• Further research may elucidate the specific pathogenesis and optimal treatment strategies for this rare variant.