How to Discern Folliculotropic Mycosis Fungoides From Follicular Mucinosis Using a Pediatric Case.

Folliculotropic mycosis fungoides (FMF) is a variant of mycosis fungoides (MF) with folliculotropic, atypical lymphocytes that may or may not have mucin deposition surrounding the hair follicle. Follicular mucinosis (FM) is a primary or secondary finding in FMF, lupus, or collagen vascular diseases that is only a histological process of mucin deposition surrounding the hair follicles. We present a case of a 6-year-old boy who had features of both FMF and primary follicular mucinosis (PFM). The case reveals key insights on FMF with concurrent FM in pediatric patients and how to differentiate between FMF and PFM.