A Challenging Eruption in a Child: A Case Report of Pityriasis Lichenoides et Varioliformis Acuta

Inflammatory skin eruptions are common in dermatology. Pityriasis Lichenoides (PL) is a rare heterogeneous dermatosis with unclear etiology, potentially triggered by infections, vaccines, medications or immune dysregulation. The acute form, Pityriasis Lichenoides et Varioliformis Acuta (PLEVA), presents with sudden papular eruptions that may undergo central necrosis and sometimes resolving with scarring. Diagnosis and management, especially in children, are challenging. Although a few adult cases temporally associated with COVID-19 vaccination have been described, pediatric reports are still scarce. We present a 9-year-old boy with a 2.5-month history of erythematous papular and maculo-purpuric lesions on the face and limbs. Fifteen days prior to the onset of the eruption, he had received the first dose of a mRNA COVID-19 vaccine. The patient initially received antibiotics for presumed impetigo and varicella, with no improvement. Physical examination revealed lesions with central crusting, while extensive laboratory investigations were unremarkable. Skin biopsy confirmed the diagnosis of PLEVA. Topical corticosteroids and tacrolimus provided partial improvement, but a subsequent flare required systemic cyclic oral azithromycin, leading to complete resolution after eight cycles. A relapse four months later was successfully treated with narrowband UVB phototherapy This case highlights the diagnostic and therapeutic challenges of PLEVA, particularly in children. It also reinforces the importance of clinical suspicion and skin biopsy in atypical or treatment-resistant eruptions. While the temporal association with mRNA COVID-19 vaccination supports a possible trigger, the incidence of such reactions remains exceedingly low relative to the global scale of vaccination. The condition remains rare and should not generate alarm or vaccine hesitancy.