[PET-CT documented complete remission of Erdheim-Chester disease, lasting more than 4 years from treatment initiation with cladribine].

Erdheim-Chester disease is a very rare histiocytic disease. It represents one form of juvenile xanthogranuloma in WHO classification of blood diseases. The disease often causes B symptoms, skeletal pain and also may cause diabetes insipidus and retroperitoneal fibrosis. Selection of therapy depends on published case reports and small clinical trials. There are no recommendations for treatment based on randomized studies. Interferon α is probably the most commonly used drug for this disease. Some remissions have been described after treatment. However, long-term interferon α application is needed which is associated with numerous side effects. There are limited experiences with clabridine in this indication. In Pubmed Medline database, we have found 3 publications dedicated to description of treatment response after cladribine in Erdheim-Chester disease and other 7 papers evaluating effect of cladribine on juvenile xanthogranuloma forms, mostly with positive outcome. Based on these 10 publications we choose cladribine as first-line treatment in our patient. The treatment started in October 2009 with combination of 2-chlorodeoxyadenosine (Litak) 5 mg/m2 sc. + cyclophosphamide 150 mg/m2 iv. + dexamethasone 24 mg iv., five days consecutively. These cycles were repeated monthly. Mentioned formula was submitted 4 times and 3 times in limited application on day 1 - 3. The reason of that was neutropenia grade 3. All symptoms disappeared after treatment. Only diabetes insipidus persisted because damage of pituitary stalk is irreversible. Therapeutic effect was monitored by PET-CT imaging, initially every 6 months, later in 12-month intervals. PET-CT imaging showed complete remission of disease and 4.5 years duration of remission after treatment. The treatment was well tolerated with no complications implying hospitalization. Only mild thrombocytopenia and neutropenia remains after 4.5 years. Based on case report and publications we consider cladribine as appropriate firs-line drug for Erdheim-Chester disease. Therapeutic failure after 3-4 cycles may suggest other options (interferon α, anakinra, vemurafenib), but only in the case if healthcare provider is willing to cover this new and more expansive treatment than therapy with cladribine.