In general, the cause of Langerhans Cell Histiocytosis is unknown. Regardless of the subtype of Langerhans cell histiocytosis, the pathologic hallmark for all subtypes of LCH is the abnormal proliferation and accumulation of immature Langerhans cells, macrophages, lymphocytes, and eosinophils. The collection of these cells is what forms granulomatous lesions. Histiocytes, a type of white blood cell, are part of the body's immune system. When produced in excess, like in LCH and LSD, they attack the body's systems and cause the physical manifestations that are seen in these patients. There have been associated gene mutations linked to Abt-Letterer-Siwe disease. LSD, in addition to all forms of LCH, is an oncogene-driven cancer of myeloid lineage. Activation of the RAS-RAF-MEK-ERK signaling pathway is seen in all patients with LCH. In 50-60% of patients with LCH, oncogenic mutations of BRAFV600E are identified. 10-15% of patients have MAP2K1 mutations. LSD has no clear association with hereditary or familial tendencies.
Letterer–Siwe disease
Fox–Fordyce disease
Brill–Zinsser disease
Paget–Schroetter disease
Laurence–Moon syndrome
Kapur–Toriello syndrome
Degos disease
Landau–Kleffner syndrome