An Unusual Juvenile Xanthogranulomaon a Finger MCP Joint.

Juvenile xanthogranuloma (JXG) is a benign self-limited histiocytic proliferative disorder that usually occurs in early childhood. JXG appears as reddish to yellow, papules, or nodules, and although the head, neck, and trunk are the most frequent locations, it can occur at any body site. However, JXG involving the finger is rare. Histologically, JXG is characterized by an ill-defined, unencapsulated, dense histiocytic infiltrate within the dermis, some of which is contained in Touton giant cells, foreign body giant cells and foamy cells. Because the cutaneous lesions spontaneously regress, treatment is not usually indicated. The authors report a case of JXG in a 4-year-old girl who had tender, yellowish papule on the ventral aspect of the MCP joint of the right fourth finger consistent with JXG.