Childhood lymphomatoid papulosis Type D, a rare and challenging diagnosis.

A 10-year-old female with a several-year history of pityriasis lichenoides (PL) presented with a new, asymptomatic, large, and necrotic ulcer of her right upper arm. Skin biopsy was consistent with lymphomatoid papulosis (LyP) Type D, a recently recognized subtype of LyP that is distinguished histologically by marked epidermotropism and a perivascular infiltrate of medium-sized pleomorphic lymphocytes with a cytotoxic phenotype (CD3+, CD8+). This is only the sixth reported case of LyP Type D in a child, and while the prognosis in children appears favorable, with no reports of progression to lymphoma to date, more experience in children with longer-term follow-up is needed. Our case highlights both the challenging clinical diagnosis, since in our patient the longstanding clinical presentation was indistinguishable from PL, as well as histopathologic diagnosis, which required expert opinion and consensus.