Sandbox: Langerhans: Difference between revisions
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:* Fibrosis | :* Fibrosis | ||
:* Other inflammatory cells may be present (neutrophils, plasma cells, and multinucleated giant cells) | :* Other inflammatory cells may be present (neutrophils, plasma cells, and multinucleated giant cells) | ||
* On electron microscopy Langerhans cell histiocytosis is characterized by Birbeck granules, which are electron dense, cytoplasmic, tennis racket-like bodies. | |||
* On immunohistochemistry Langerhans cell histiocytosis is characterized by: | |||
:* CD1a +ve | |||
:* S100 +ve | |||
:* CD207 (Langerin) +ve |
Revision as of 19:03, 2 February 2016
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 malignant Langerhans cells will lead to a deficiency in both anterior and posterior pituitary hormones, which may result in:
- Central diabetes insipidus
- Growth retardation
- Delayed puberty
- Langerhans cell histiocytosis may also infiltrate the lymph nodes, spleen, and liver.
Genetics
- Development of Langerhans cell histiocytosis is the result of multiple genetic mutations.
- Genes commonly involved in the pathogenesis of Langerhans cell histiocytosis include:
- BRAF gene mutation located on Chromosome 7
- MAP2K1 gene mutation located on Chromosome 15
Associated Conditions
- Langerhans cell histiocytosis is associated with a number of syndromes that include:
- Hand-Schüller-Christian triad
- Hashimoto-Pritzker disease
- Letterer-Siwe disease
Gross Pathology
- On gross pathology, scaly erythematous, red papules, and extensive eruptions located on the scalp are characteristic finding of Langerhans cell histiocytosis.
- The image below demonstrates the cutaneous lesions observed among Langerhans cell histiocytosis patients:
Microscopic Pathology
- Characteristic findings of Langerhans cell histiocytosis on light microscopy may include:
- Langerhans cells histiocytes
- Clusters of cells
- Kidney-shaped nucleus
- Abundant foamy cytoplasm
- Fine, granular chromatin pattern
- Prominent eosinophils
- Fibrosis
- Other inflammatory cells may be present (neutrophils, plasma cells, and multinucleated giant cells)
- On electron microscopy Langerhans cell histiocytosis is characterized by Birbeck granules, which are electron dense, cytoplasmic, tennis racket-like bodies.
- On immunohistochemistry Langerhans cell histiocytosis is characterized by:
- CD1a +ve
- S100 +ve
- CD207 (Langerin) +ve