Being “Puzzled” as the First Step to Diagnosis

TAKE-HOME LEARNING POINTS
• Lichen planus (LP) is common and typically presents on the volar wrists, dorsal ankles, and sacrum.

• In a minority of cases, LP can present on the legs as a hypertrophic, plaquish condition with secondary features of lichen simplex chronicus. 

• A mnemonic device (“The Ps”) describes LP: papular, pruritic, purple, planar, polygonal, plaquish, and (perhaps most importantly) “puzzling.”

• LP can present as an annular plaque on the penile glans. 

• LP has a pathognomic histologic picture on biopsy.