Pityriasis Lichenoides: PLEVA and PLC

Overview / Definition Pityriasis lichenoides is an uncommon inflammatory skin disorder that presents in two distinct forms: Pityriasis Lichenoides et Varioliformis Acuta (PLEVA) and Pityriasis Lichenoides Chronica (PLC). PLEVA is characterized by acute eruptions that can lead to vesiculation and ulceration, while PLC is a more chronic, indolent form that presents with papules and scaling. Epidemiology Pityriasis lichenoides is relatively rare, with PLEVA more commonly seen in children and young adults, while PLC tends to affect adults more frequently. The incidence rates vary by geographic region and population, but overall, it remains a low-prevalence condition. PLEVA is more prevalent in males. Incidence peaks in individuals aged 10-30 years. PLC has a broader age range but is predominantly seen in adults. Pathophysiology / Mechanism The exact etiology of pityriasis lichenoides remains unclear, but it is thought to involve an abnormal immune response, possibly triggered by viral infections, medications, or other environmental factors. Both forms are associated with a dysregulation of keratinocyte apoptosis and inflammatory responses. Possible viral triggers include Epstein-Barr virus (EBV). Drug-induced cases have been reported, particularly with antibiotics and anti-inflammatory medications. Histological examination shows a lichenoid tissue reaction with interface dermatitis. Clinical Presentation Clinically, PLEVA presents with erythematous papules that may progress to vesicles and crusted lesions, often resembling varicella. Lesions are typically found on the trunk and extremities and can be pruritic. In contrast, PLC manifests as small, brownish papules that are often asymptomatic and may be widespread. PLEVA can be acute with rapid onset and may lead to systemic symptoms. PLC tends to have a chronic course with intermittent flares. Lesions may resolve spontaneously, but residual pigmentation can occur. Diagnosis / Workup Diagnosis is primarily clinical, suppo