non-tumourous lesions, there is a symmetrical hyperintense T2 signal with hypointense or hyperintense T1 signal extending from grey matter into the white matter. In the basal ganglia, MRI shows a hyperintense T1 signal in the globus pallidus. Assessment of endocrine function and bonemarrow biopsy are also performed when indicated. S-100 protein is expressed in a cytoplasmic pattern peanut agglutinin (PNA) is expressed on the cell surface and perinuclearly major histocompatibility (MHC) class II is expressed (because histiocytes are macrophages) CD1a langerin (CD207), a Langerhans Cell–restricted protein that induces the formation of Birbeck granules and is constitutively associated with them, is a highly specific marker. Treatment Guidelines for management of patients up to 18 years with Langerhans cell histiocytosis have been suggested. Treatment is guided by extent of disease. Solitary bone lesion may be amenable through excision or limited radiation, dosage of 5-10 Gy for children, 24-30 Gy for adults. However systemic diseases often require chemotherapy. Use of systemic steroid is common, singly or adjunct to chemotherapy. Local steroid cream is applied to skin lesions. Endocrine deficiency often require lifelong supplement e.g. desmopressin for diabetes insipidus which can be applied as nasal drop. Chemotherapeutic agents such as alkylating agents, antimetabolites, vinca alkaloids either singly or in combination can lead to complete remission in diffuse disease. Prognosis There is a general excellent prognosis for the disease as those with localized disease have a long life span. With multi-focal disease 60% have a chronic course, 30% achieve remission and mortality is up to 10%.A full recovery can be expected for people who seek treatment and do not have more lesions at 12 and 24 months. However, 50% of children under 2 with disseminated Langerhans cell histiocytosis die of the disease. The prognosis rate decreases for patients who experience lung involvement. Whereas patients with skin and a solitary lymph node involvement generally have a good prognosis. Although there is a general good prognosis for Langerhans cell histiocytosis, approximately 0% of patients with the disease are prone to various complications such as musculoskeletal disability, skin scarring and diabetes insipidus. Prevalence LCH usually affects children between 1 and 15 years old, with a peak incidence between 5 and 10 years of age. Among children under the age of 10, yearly incidence is thought to be 1 in 200,000; and in adults even rarer, in about 1 in 560,000. It has been reported in elderly but is