Clinical and clonal characteristics of monoclonal immunoglobulin M‐associated type I cryoglobulinaemia

Abstract

SummaryMonoclonal immunoglobulin M‐associated type I cryoglobulinaemia is poorly characterised. We screened 534 patients with monoclonal IgM disorders over a 9‐year period and identified 134 patients with IgM type I cryoglobulins. Of these, 76% had Waldenström macroglobulinaemia (WM), 5% had other non‐Hodgkin lymphoma (NHL) and 19% had IgM monoclonal gammopathy of undetermined significance (MGUS). Clinically relevant IgM‐associated disorders (including cold agglutinin disease [CAD], anti‐MAG antibodies, amyloidosis and Schnitzler syndrome) coexisted in 31%, more frequently in MGUS versus WM/NHL (72% vs. 22%/29%, p < 0.001). The majority of those with cryoglobulins and coexistent CAD/syndrome had the molecular characteristics of a CAD clone (wild‐type MYD88 in 80%). A half of all patients had active manifestations at cryoglobulin detection: vasomotor (22%), cutaneous (16%), peripheral neuropathy (22%) and hyperviscosity (9%). 16/134 required treatment for cryoglobulin‐related symptoms alone at a median of 38 days (range: 6–239) from cryoglobulin detection. At a median follow‐up of 3 years (range: 0–10), 3‐year cryoglobulinaemia‐treatment‐free survival was 77% (95% CI: 68%–84%). Age was the only predictor of overall survival. Predictors of cryoglobulinaemia‐related treatment/death were hyperviscosity (HR: 73.01; 95% CI: 15.62–341.36, p < 0.0001) and cutaneous involvement (HR: 2.95; 95% CI: 1.13–7.71, p = 0.028). Type I IgM cryoglobulinaemia is more prevalent than previously described in IgM gammopathy and should be actively sought.