PMC9833300_01
Histologic features of the B-cell and plasma cell component, consistent with gamma-heavy chain disease. CD138 (A) and CD20 (A, inset) show a mild, interstitial infiltrate made up of mature plasma cells and small B-lymphocytes. The plasma cell component is positive for IgG (B) but does not express light chains (C: kappa; D: lambda).
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BM biopsy identified 20% interstitial infiltrate of small B-lymphocytes CD20+/CD5-/CD23-/CyclinD1-/DBA.44-/IgM-/IgD along with mature plasma cells CD138 and IgG positive and negative for IgM, IgD and both kappa and lambda light chains, similarly as observed with flow cytometry (Figure 1a). Moreover, an additional 10% interstitial and intrasinusoidal T-cell infiltrate CD3+, CD8+, CD57+/-, and CD4- consistent with T-LGL expansion was found (Figure 1b).
Serum electrophoresis (A) and serum immunofixation (B).
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Serum electrophoresis showed hypo-gammaglobulinemia at 0.35 g/dL with increased alfa-2-region at 1.6 g/dL but no clear monoclonal component (Figure 3a). Nevertheless, serum immunofixation identified a monoclonal IgG heavy chain without corresponding light chains (Figure 3b), also present in the urine, according to flow cytometric analysis.