Diagnosing<unk>  requires a complete work-up and examination because its symptoms are often non-specific and appear like other benign conditions. A diagnosis of LSD can be made with positive biochemical findings suggestive of LSD in addition to evidence of multi-organ involvement. The diagnosis is established by biopsy. Pathology then uses immunohistochemical characteristics, such as cell surface markers CD1a, CD207, and S-100, to help identify the Langerhans cells. Because of the link LCH has to BRAFV600E and other MAPK pathway mutations, tumor tissue should be tested for associated mutations. Electron microscopy will show racket-like Langerhans cell granules within the specific infiltrating cells. The demonstration of these organelles allows the unequivocal diagnosis in cases with uncharacteristic clinical or histopathological appearance. The same structures are characteristic of Hand-Schüller-Christian disease and of eosinophilic granuloma. The electron microscopic findings confirm the grouping of these three diseases together as "histiocytosis X". In order to evaluate the degree of organ involvement in these patients, physicians may conduct a variety of diagnostic tests, such as In addition, a work-up for congenital and acquired immunodeficiency syndromes should be completed. In addition, a work-up should be done on potential infectious etiologies. LSD may easily be missed for other conditions causing anemia, thrombocytopenia, and hepatosplenomegaly, but should be considered especially if the patient's disease course has been refractory to antibiotics.
Letterer–Siwe disease
Fox–Fordyce disease
Brill–Zinsser disease
Paget–Schroetter disease
Laurence–Moon syndrome
Kapur–Toriello syndrome
Degos disease
Landau–Kleffner syndrome