[Skin involvement in Rosai-Dorfman disease. Description of a case].

Sinus Histiocytosis with massive lymphadenopathy is an idiopathic, histologically distinctive disorder that characteristically produces painless cervical lymphadenopathy. Other node groups are frequently involved and mass lesions in extranodal sites occur in approximately 30% of patients. In most cases the disease is chronic and the course is often characterized by exacerbations and remission. We report the case of a 66 years old white woman affected by sinus histiocytosis with massive cervical and inguinal lymphadenopathy. Subcutaneous nodules appeared in her left arm and low back region with the histological features of sinus histiocytosis. Cellular infiltrate was composed predominantly of histiocytes aggregating in granuloma like clusters. These cells had large round or kidney shaped nuclei; cytoplasm was abundant, vacuolated, often containing phagocytized lymphocytes. Multinucleated cells were also observed; reactive plasmocytosis was present in the nodule periphery. During the follow-up the patient maintained good physical conditions, despite a moderate weight loss. The size of her nodules regressed within one year. Immunologic alterations, consisting of polyclonal hypergammaglobulinemia and persistent inversion of T4/T8 lymphocyte ratio, were observed. Sinus histiocytosis usually offers a good prognosis; in our patient infective and/or autoimmune complications could be favoured by advanced age, extranodal involvement and immunological depression.