Walsdenström Macroglobulinemia (WM) is defined by a bone marrow lymphoplasmacytic infiltration and the presence of a monoclonal immunoglobulin M (IgM) in blood. Clinical manifestations of the hyperviscosity syndrome (HVS) are related to the large amount of IgM in circulating blood or to some physicochemical characteristics such as the presence of a cryoglobulin property. Although HVS is one of the most frequent criteria for initiating therapy in WM, few studies focused on its description and no diagnostic criteria are available.

The present study aims to identify a diagnostic system for HVS, taking into account objective symptoms such as bleedings, fundoscopic findings and also subjective symptoms such as fatigue and comorbidities that may influence the severity of symptoms.

Inclusion Criteria:

• Patient with WM
• Patients that may require a first-line or subsequent-line therapy
• patients who will require treatment initiation
• patients with serum monoclonal component concentration greater than 15 g/L and who will underwent hyperviscosity assessment, even if hyperviscosity is not found and in the absence of other treatment criteria, no treatment is finally initiated.
• Patients agreeing to give informed consent.

Exclusion Criteria:

• Patients with another chronic B-cell malignancy
• patients with lymphoplasmacytic proliferations
• patients with marginal zone lymphoma.
• patients with WM and histologic transformation
• Absence of informed consent.