<s>[INST] <<SYS>> This is a medical question of type : exams and tests <</SYS>> How to diagnose Pityriasis lichenoides et varioliformis acuta ? [/INST] How is pityriasis lichenoides et varioliformis acuta diagnosed? A diagnosis of pityriasis lichenoides et varioliformis acuta is often suspected based on characteristic signs and symptoms. A skin biopsy can be used to confirm the diagnosis. Additional laboratory testing may be ordered to investigate a possible cause such as an associated infection. </s>