Diffuse (Generalized) Plane Xanthoma Misdiagnosed as Carotenoderma: Usefulness of Reflectance Confocal Microscopy.

Diffuse (generalized) plane xanthoma is a rare normolipemic xanthomatosis, frequently associated with multiple myeloma and monoclonal gammopathy. Its clinical presentation is well described, and in most cases, clinical suspicion is immediate. Rarely, it can clinically present with a diffuse and uniform yellowish discoloration, and in this context, several investigations are required to identify the correct diagnosis. We describe a case characterized by progressive diffuse yellow-orange discoloration lasting about 3 years and classified as carotenoderma in which reflectance confocal microscopy addressed the diagnosis and drove the correct selection of the biopsy site. Definitive diagnosis of diffuse (generalized) plane xanthoma was confirmed later by histological examination.