Waldenström macroglobulinemia

Waldenström macroglobulinaemia is a subtype of lymphoplasmacytic lymphoma (LPL), a form of B-cell lymphoma.

Terminology

Recent publications classify Waldenström macroglobulinaemia is classified as a subtype of lymphoplasmacytic lymphomawith any level of an IgM paraprotein; these two conditions are not synonymous ¹⁰.

Epidemiology

It is a rare condition, accounting for only 1% of all lymphoproliferative disorders. The incidence is 1500 cases per year in the United States. The median age of onset is 60-65 years. A minority of cases occur in late adolescence.

Clinical presentation

Most patients are asymptomatic at the time of diagnosis, which is often incidentally made during blood tests for an unrelated condition. If symptoms occur, the most common ones are fatigue (2/3 of cases) and and polyneuropathy (1/4 of cases). Otherwise, the presentation includes the triad of non-specific B-symptoms: fever, night sweats, and unintentional weight loss. Another feature is hyperviscosity syndrome.

Another recognised presentation is Schnitzler syndrome: where Waldenström macroglobulinaemia manifests as an urticarial skin vasculitis.

Pathology

The pathogenesis is poorly understood but may resemble that of chronic lymphocytic leukaemia. Clonal proliferation of functionally impaired B-cells occurs, as well as infiltration of various tissues (predominantly bone marrow, spleen, and lymph nodes). There is an overproduction of IgM, leading to hyperviscosity syndrome and resultant impaired microcirculation.

Radiographic features

There have been relatively few articles on the imaging features of Waldenström macroglobulinaemia. Authorities do not recommend imaging as part of the initial workup of patients ¹⁴.

MRI

Bone marrow involvement is the most common imaging manifestation, best appreciated on MRI. One study found that MRI spines were abnormal in 91% of cases with two main appearances seen ¹⁴:

• diffuse: all bone marrow signal is abnormal

• heterogeneous: myriad small foci of abnormal signal scattered throughout uninvolved bone marrow

Treatment and prognosis

The International Prognostic Scoring System for Waldenström macroglobulinaemia is a predictive model for characterisation of long-term outcome. Factors predicting survival are:

• age >65 years

• haemoglobin ≤11.5 g/dL

• platelet count ≤100 x 10⁹/L

• B2-microglobulin >3 mg/L

• serum monoclonal protein concentration >70 g/L

Risk categories are:

• low: ≤1 adverse variable except age

• intermediate: 2 adverse characteristics or age >65 years

• high: >2 adverse characteristics

Five-year survival rates for these categories are 87%, 68%, and 36% respectively.

Untreated, the disease typically progresses indolently, and behaves differently among patients.

Complications

• Bing-Neel syndrome: malignant lymphocyte infiltration into the central nervous system (CNS) ^11 11

History and etymology

This condition was first described in 1944 by Swedish haem-oncologist Jan Gosta Waldenström (1906-1996) ^1,12.