Histiocytosis X Hand-Schuller-Christian Syndrome In this disease of the immune system, abnormal scavenger cells called histiocytes and eosinophils (another immune system cell type) grow uncontrollably, proliferating usually in the lungs and bone, often forming scars that interfere with normal functioning. These cells constitute malignant or benign macrophages in the tissues, or Langerhans' cells in the bone marrow. This syndrome is characterized by three, simultaneous conditions: Diabetes Insipidus Exopthalmus Destructive Bone Lesions Diabetes Insipidus is a condition in which the body fails to produce the hormone vasopressin (anti-diuretic hormone), or the kidneys fail to use vasopressin properly.  The result is loss of large volumes of water through excretion (urination).  Exophthalmos means protrusion of the globe of the eye (i.e., the "eyeball" protrudes).  It is caused by damage to the pituitary gland. Hand-Schuller-Christian syndrome often occurs with lymphoma, carcinoma, and multifocal eosinophilic granuloma (it occurs in 25% of all cases of multifocal eosinophilic granuloma). Treatment involves treating the underlying cause, such as lymphoma, and manifestations, such as diabetes insipidus.  See sections on specific underlying diseases and/or manifestations for more details.