[Erdheim-Chester disease-A histiocytic multisystem disease with unusual renal involvement]

Erdheim-Chester disease (ECD) is nowadays classified as belonging to those neoplasms with origins in the myeloid dendritic cell lines. The clonal alterations maintain a chronic inflammatory condition, which dominates the pathogenesis and clinical expression. Characteristic for ECD are many skeletal manifestations; however, the multisystem disease affects many other organs (including the respiratory tract, heart, retroperitoneum, eyes, central nervous system and endocrine system). The diagnosis is usually first made only after a disease duration of many years. This is due to the rarity of the disease and the very diffuse symptoms in addition to the heterogeneous organ manifestations. There are no uniform diagnostic criteria. The constellation of unclear polyserositis and ostealgia, possibly in association with neurological and endocrine deficiencies, should steer the suspicion towards an ECD. The diagnosis can be confirmed by an organ biopsy and the immunohistochemical examination enables the relatively certain differentiation from other forms of histiocytosis. The detection of activating oncological mutations in signal transduction pathways has opened up the possibility of targeted treatment with kinase inhibitors, such as vemurafenib for BRAF V600E mutations. Up to the discovery of activating mutations, interferon-alpha was used as the first line treatment; however, in view of the superiority of kinase inhibitors, the first line treatment with interferon-alpha currently appears to be questionable. The prognosis for untreated ECD is exceptionally poor and interferon-alpha leads to a clear improvement. Further progress is hoped for with the use of targeted treatments.