Primary adult-onset macrophage activation syndrome with multisystemic tissue phagocytosis.

The histiocyte disorders are divided into the following 3 categories according to the specific lineage of the histiocytes involved and their biological behavior: the dendritic cell-related disorders, which include Langerhans cell histiocytosis and dermal dendrocyte disorders; the macrophage cell disorders, hemophagocytic lymphohistiocytosis being the main entity; and the malignant histiocyte disorders. We present a case of a 36-year-old woman who was referred to our hospital because of fever of unknown origin, lethargy, anemia, and impaired hepatic function. Following a thorough investigation, we diagnosed extensive histiocyte-mediated phagocytosis in many areas (skin, liver, bone marrow), without any identifiable cause. The disease was controlled by immunosuppressive therapy, and the patient remains in complete remission. This case supports the concept of idiopathic generalized histiocyte activation as a distinct entity; this putative disease entity produces massive phagocytosis, regardless of the type of histiocyte differentiation. Similar cases necessitate further study for classification and management.