PLCH develops when an abundance of monoclonal CD1a-positive Langerhans (immature histiocytes) proliferate the bronchioles and alveolar interstitium, and this flood of histiocytes recruits granulocytes like eosinophils and neutrophils and agranulocytes like lymphocytes further destroying bronchioles and the interstitial alveolar space that can cause damage to the lungs. It is hypothesized that bronchiolar destruction in PLCH is first attributed to the special state of Langerhans cells that induce cytotoxic T-cell responses, and this is further supported by research that has shown an abundance of T-cells in early PLCH lesions that are CD4+ and present early activation markers. Some affected people recover completely after they stop smoking, but others develop long-term complications such as pulmonary fibrosis and pulmonary hypertension. Signs and symptoms
LCH provokes a non-specific inflammatory response, which includes fever, lethargy, and weight loss. Organ involvement can also cause more specific symptoms. Bone: The most-frequently seen symptom in both unifocal and multifocal disease is painful bone swelling. The skull is most frequently affected, followed by the long bones of the upper extremities and flat bones. Infiltration in hands and feet is unusual. Osteolytic lesions can lead to pathological fractures. Skin: Commonly seen are a rash which varies from scaly erythematous lesions to red papules pronounced in intertriginous areas. Up to 80% of LCH patients have extensive eruptions on the scalp. Bone marrow: Pancytopenia with superadded infection usually implies a poor prognosis. Anemia can be due to a number of factors and does not necessarily imply bone marrow infiltration.
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
Excellent for single-focus disease. With multi-focal disease 60% have a chronic course, 30% achieve remission and mortality is up to 10%. 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.