Israel Medical Association Journal

Histiocytosis of childhood is characterized by localized or generalized proliferation of cells of the mononuclear phagocyte system and the dendritic cell system. In patients with Langerhans cell histiocytosis, the orbita is the most involved site encountered in ophthalmic practice, usually as a lytic lesion in the zygomaticofrontal suture. Patients usually present with acute or chronic periorbital swelling. Electron microscopic findings of Birbeck granules and positive staining for CD1 antigenic determinant confirm the diagnosis.

Hemophagocytic lymphohistiocytosis is thought to occur as a primary (familial) form or secondary to infection or malignancy. Recently, several defects in genes important for immune functions were identified in patients with HLH[1]. These include mutations in perforin, the gamma common chain, the receptor for interleukin-2, Slap and purine nucleoside phosphorylase. Since abnormal function of these genes is associated with a wide clinical spectrum, HLH is probably another manifestation of immune deficiency and a thorough immune evaluation should be done in all such patients.