Inclusion Criteria:

- patients >= 18 years of age able to understand and sign an informed consent;

- histologically proven diagnosis of Erdheim-Chester disease ;

- an advanced disease not limited to the skeleton, with at least one measurable lesion;

- if females of childbearing potential, a negative pregnancy test and willingness to
adhere to a highly effective contraceptive method of birth control for the duration
of the study;

Exclusion Criteria:

- history of hypersensitivity to tocilizumab or to any of the excipients;

- severe infections requiring hospitalization or antibiotic therapy in the 30 days
before the enrollment in the study;

- active tuberculosis, listeriosis, histoplasmosis, sepsis, abscesses, opportunistic
infections; active hepatitis B or C virus infection;

- past history of tuberculosis (as documented by a positive purified protein derivative
(PPD) skin test and/or a positive Quantiferon test and/or a chest X- ray), in the
absence of a documented and appropriate administration of a specific treatment for
latent tuberculosis;

- history of human immunodeficiency virus (HIV) infection;

- past history (< 5 years before enrollment) of a lymphoproliferative disorder or of a
solid cancer (excluding cured basal cell or squamous cell carcinoma of the skin);

- moderate or severe heart failure (NYHA class III/IV), uncontrolled diabetes mellitus
or other diseases that -according to the physician in charge of the protocol- may be
of harm to the patient, if he/she would enroll in the study;

- history of alcohol and/or drug abuse;

- prior treatment with alkylating drugs (chlorambucil, cyclophosphamide);

- serum creatinine > 1.6 mg/dL in female patients or > 1.9 mg/dL in male patients,
aspartate aminotransferase and/or alanine aminotransferase > 3 x upper limit of
normal ; platelet < 100.000/fL; hemoglobin < 8.5 g/dL; white blood cell count <
1000/fL; lymphocyte < 500/fL; total bilirubin > 2.0 mg/dL