Both clonal plasma cell and myeloid disorders occur more frequently with age. Patients with concurrent clonal plasma cell and myeloid disorders (CPCMD) can present clinical and therapeutic challenges. In this single-institution cohort of patients with CPCMD (n = 18), we abstracted clinically relevant themes. A majority of patients (12/18) were treated with clone-directed therapies and three received treatment targeting both clones. Treatment of clones with targetable genetic lesions or those causing end-organ complications should be prioritized. Simultaneous treatment of both clones can be safe but is best done in a stepwise manner. Further study of patients with dual clonal processes is warranted.

IgG4-related diseases (IgG-RDs) are a group of fibroinflammatory diseases that affect a variety of tissues, resulting in tumour-like effects and/or organ dysfunction. Monoclonal gammopathies (MGPs) are a group of disorders characterized by clonal proliferation of plasma cells or lymphoid cells resulting in the secretion of a monoclonal immunoglobulin. Cases of MGPs in IgG4-RDs coexisting with plasma cell dyscrasias and lymphoid neoplasms have been reported over the past few years. Therefore, the results of examinations of M protein in IgG4-RD patients should be interpreted with caution. Herein, we report the case of a 58-year-old male with a history of type 2 diabetes who presented with submandibular masses, anosmia, swollen lymph nodes, proteinuria, and renal impairment. Laboratory tests revealed hyperglobulinemia and elevated levels of IgG4 (124 g/L) and serum-free light chains (sFLCs). Serum protein electrophoresis (SPEP) revealed an M spike of 5.6 g/dL, and immunofixation electrophoresis (IPE) revealed biclonal IgG-κ and IgG-λ. The patient underwent bone marrow, lymph node, and kidney biopsy, which ruled out plasma cell disorders and lymphoma. He was finally diagnosed with an IgG4-RD comorbid with diabetic nephropathy. The findings in this case highlight that significant activation of B cells in IgG4-RD patients, especially those with multiorgan involvement can lead to significant hyperglobulinemia and high sFLC and IgG4 levels, which are more pronounced in the setting of renal impairment. Relatively high concentrations of polyclonal IgG4 can give rise to a focal band bridging the β and γ fractions, which may mimic the appearance of a monoclonal band on SPEP and monoclonal gammaglobulinemia in IFE. The patient experienced considerable improvement in his symptoms after rituximab combined with glucocorticoid therapy, and a monoclonal immunoglobulin was not detected.

BACKGROUND: Multiple myeloma (MM) can be accompanied by amyloidosis, which occurs in a small number of patients and is characterized by deposition of light chains in the joints, leading to multiple myeloma-associated amyloid arthropathy (MAA). As a rare complication of MM, clinical manifestations of MAA are often similar to those of rheumatoid arthritis, and the two are easily confused.
METHODS: In recent years, our center treated two patients of MM with amyloid arthropathy as the first manifestation, both of whom presented with polyarthritis. After treatment for MM, both patients achieved complete remission. However, subsequently, the two patients underwent hip arthroplasty for femoral neck fractures. Congo red staining and immunofluorescence of the joint tissues confirmed MAA after surgery. Eventually, one of the patients died of MM recurrence, while the other survived.
CONCLUSIONS: MAA should be regarded as an initial symptom of MM and should be taken seriously.

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Conduct in case of monoclonal gammapathy ? Monoclonal gammopathies are frequent in general population (about 3 % beyond 50 years) and their prevalence increases with age. They may be associated with malignant haemopathy (multiple myeloma for IgG and IgA, Waldenström disease for IgM). In absence of malignant haemopathy, the diagnosis is that of monoclonal gammopathy of indeterminate significance (MGUS). MGUS accounts for the majority (over 60 %) cases of monoclonal gammopathy. Only patients with multiple myeloma or Waldenström disease require treatment. For MGUS, smoldering myeloma and smoldering Waldenström disease, therapeutic abstention is recommended but regular and prolonged monitoring is necessary given the risk of progression to malignant hemopathy. Given the prevalence of monoclonal gammopathies in general population and the frequency of MGUS, it is rational to limit initial explorations in asymptomatic patients.
Conduite à tenir devant une gammapathie monoclonale ? Les gammapathies monoclonales sont fréquentes dans la population générale (environ 3 % au-delà de 50 ans), et leur prévalence augmente avec l’âge. Elles peuvent être révélatrices d’une hémopathie maligne (myélome multiple pour les immunoglobulines [Ig] IgG et IgA, maladie de Waldenström pour les IgM). Lorsqu’une hémopathie maligne est éliminée, le diagnostic retenu est celui de gammapathie monoclonale de signification indéterminée (MGUS). Ces dernières représentent la majorité (plus de 60 %) des cas de gammapathie monoclonale. Seuls les patients ayant un myélome multiple ou une maladie de Waldenström relèvent d’un traitement. Pour les gammapathies monoclonales de signification indéterminée, les myélomes indolents et les maladies de Waldenström indolentes, l’abstention thérapeutique est préconisée, mais une surveillance régulière et prolongée est nécessaire compte tenu du risque de progression vers une hémopathie maligne. En raison de la prévalence des gammapathies monoclonales dans la population générale et de la fréquence de celles de signification indéterminée, il paraît légitime de limiter les explorations initiales chez les patients asymptomatiques.