Familial histiocytic dermatoarthritis. Histologic and ultrastructural findings in two cases

We report the clinical, histological, and ultrastructural study of two patients, mother and daughter, 32 and six years old, respectively, who presented with dermatitis and arthritis. From the clinical point of view, they appeared to be affected by Familial Histiocytic Dermatoarthritis (FHD), a diagnosis supported by the early age of onset, familial occurrence, and a typical ocular lesion in the mother (glaucoma, uveitis, and cataracts). However, histology revealed the presence of multinucleated giant cells that are usually associated with Multicentric Reticulohistiocytosis (MR). Unlike MR, in the cases here reported the PAS positive, intracytoplasmic material appeared to be glycogen. Electron microscopy disclosed pleomorphic bodies, which have also been described in MR. Thus, we conclude that FHD and MR probably do not represent separate entities, and that a spectrum of disorders exists between these two conditions.