Sandbox: Langerhans
Overview
Pathogenesis
- Langerhans cell histiocytosis arises from epidermal dendritic cells, which are normally involved in the process of antigen presentation to lymphocytic cells.
- Langerhans cells originally arise from the bone marrow, then the cells migrate to other organs such as:
- Skin
- Lymph nodes
- Lungs
- Hypothalamic pituitary axis
- Gastrointestinal tract
- CNS
- Oral cavity
- The malignant organ involvement is variable among patients with Langerhans cell histiocytosis. The disease process may range from an isolated cutaneous or bone involvement to a life-threatening multi-system condition.
- The skeletal distribution of Langerhans cell histiocytosis involves the following sites:
- The skull (most common bone involved)
- Ribs
- Humerus
- Vertebra
- The exact pathogenesis of Langerhans cell histiocytosis is not fully understood. It is thought that Langerhans cell histiocytosis is the result of either a true neoplastic process or a reactive immune condition.
- Facts consistent with the neoplastic process hypothesis include the following:
- The infiltration of organs by monoclonal population of pathologic cells
- The presence of specific recurrent cytogenetic and genomic abnormalities
- The successful treatment of a subset of disseminated Langerhans cell histiocytosis using chemotherapeutic regimens
- Facts consistent with the reactive immune condition hypothesis include the following:
- The evidence of spontaneous remissions that may occur among certain cases of Langerhans cell histiocytosis
- The extensive secretion of multiple cytokines by dendritic cells and bystander-cells (a phenomenon known as cytokine storm)
- The favorable prognosis and relatively good survival rate among patients with no organ dysfunction
- The excessive Langerhans cells clonal proliferation will initiate a non-specific inflammatory response, which will lead to the accumulation of various immune system cells such as:
- Eosinophils
- Macrophages
- Lymphocytes
- Multinucleated giant cells
- Langerhans cell histiocytosis may result in bone marrow failure due to malignant cell infiltration of the bone marrow. This can manifest as:
- Anemia
- Recurrent bleeding
- Recurrent Infections
- The infiltration of the hypothalamic pituitary axis by the malignant Langerhans cells will lead to both anterior and posterior pituitary hormones deficiencies.