IgD multiple myeloma: Clinical, biological features and prognostic value of the serum free light chain assay.

IgD multiple myeloma (MM) is a rare subtype of myeloma, it affects less than 2% of patients with MM. To evaluate the clinical and prognostic attributes of serum free light chains (sFLCs) analysis, we examined 17 cases of IgD MM. From 1998 to 2012, we obtained 1250 monoclonal gammapathies including 590 multiple myeloma and 17 patients had IgD MM. With preponderance of men patients with a mean age at diagnosis of: 59±12years. Patients with IgD MM have a short survival (Median survival=9months). The presenting features included: bone pain (75%), lymphadenopathy (16%), hepatomegaly (25%), splenomegaly (8%), associated AL amyloidosis (6%), renal impairment function (82%), infections (47%), hypercalcemia (37%) and anemia (93%). Serum electrophoresis showed a subtle M-spike (Mean=13.22±10g/L) in all patients associated to a hypogammaglobulinemia. There was an over-representation of Lambda light chain (65%); high serum β2-microglobulin in 91% and Bence Jones proteinuria was identified in 71%. The median rate of sFLCs κ was 19.05mg/L and 296.75mg/L for sFLCs λ. sFLCR was abnormal in 93% of patients and it showed concordance between baseline sFLCR and the survival (P=0.034). The contribution of FLC assay is crucial for the prognosis of patients with IgD MM.