50 patients with a diagnosis of MPN will have an assessment of b2microglobuline at diagnosis and after 1 year. b2mic value decrease will be compared to treatment response.

Inclusion Criteria:

• MPN patient diagnosed at one of the participating centers
• over 18 yo

Exclusion Criteria:

• Not able to consent

Patients with a new diagnosis of MPN

All collected data that underlie results in a publication

Data will be available beginning three years and ending fifteen years following the final study report completion

Data access requests will be reviewed by the internal committee of Brest UH. Requestors will be required to sign and complete a data access agreement