Pityriasis lichenoides et varioliformis acuta https://en.wikipedia.org/wiki/Pityriasis_lichenoides_et_varioliformis_acuta
Pityriasis lichenoides et varioliformis acuta is a disease of the immune system. It represents the more severe form of pityriasis lichenoides chronica. The condition is characterized by rashes and small skin lesions. It occurs more frequently in males and typically presents in young adulthood. It is often misdiagnosed as chickenpox or a Staphylococcal infection. A biopsy is recommended for diagnosis.

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References Pityriasis Lichenoides Et Varioliformis Acuta (PLEVA) 36256784 
NIH
Pityriasis lichenoides et varioliformis acuta (PLEVA), also known as Mucha-Habermann disease, is an uncommon cutaneous inflammatory rash characterized by diffuse red-brown papules in various stages with a mica-like scale on more established lesions. The papules may progress to form vesicles, pustules, and ulcers, and these lesions can be associated with pruritus or a burning sensation. PLEVA favors the trunk and proximal extremities, especially in the flexural regions. This rash tends to relapse and remit with variable duration, sometimes lasting up to years.