Adult Presentation of Cutaneous Langerhans Cell Histiocytosis: 18 F-FDG PET/CT Detection of Systemic Disease.

Langerhans cell histiocytosis (LCH) is a rare hematological disease, more common in pediatric populations. A 26-year-old man with biopsy-proven cutaneous LCH underwent 18 F-FDG PET/CT systemic staging. 18 F-FDG PET/CT highlighted multiple sites of avid cutaneous disease within the natal cleft. Additional characteristic cystic lung disease was seen on the CT component and focal uptake in the pituitary stalk/hypothalamic region noted, a common but occult site of disease in this patient. Because of the rarity of adult-onset cutaneous LCH, guidance on management and staging is lacking. 18 F-FDG PET/CT is critical to baseline evaluation of systemic disease, as illustrated here.