Indian Journal of Pathology and Microbiology

CASE REPORT
Year
: 2017  |  Volume : 60  |  Issue : 4  |  Page : 590--592

Monoclonal gammopathy with double M-bands: An atypical presentation on serum protein electrophoresis simulating biclonal gammopathy


Kaustubh Bora1, Umesh Das2, Bhupen Barman3, Alice Abraham Ruram4,  
1 ICMR-Regional Medical Research Centre, North East Region, Dibrugarh, Assam; Department of Biochemistry, North Eastern Indira Gandhi Regional Institute of Health and Medical Sciences, Shillong, Meghalaya, India
2 Department of Medical Oncology, North Eastern Indira Gandhi Regional Institute of Health and Medical Sciences, Shillong, Meghalaya, India
3 Department of Internal Medicine, North Eastern Indira Gandhi Regional Institute of Health and Medical Sciences, Shillong, Meghalaya, India
4 Department of Biochemistry, North Eastern Indira Gandhi Regional Institute of Health and Medical Sciences, Shillong, Meghalaya, India

Correspondence Address:
Kaustubh Bora
ICMR-Regional Medical Research Centre, North East Region, Dibrugarh - 786 010, Assam
India

Abstract

Monoclonal gammopathies, such as multiple myeloma, typically exhibit high levels of a monoclonal immunoglobulin (M-protein), produced by a clone of abnormally proliferating B-lymphocytes and/or plasma cells. The M-protein can be evaluated by serum protein electrophoresis (SPEP), which yields a single discrete band (M-band), usually in the γ-globulin region. Rarely, two M-bands appear simultaneously at different positions during SPEP – a condition known as biclonal gammopathy, which is a result of clonal expansion of two different neoplastic cell lines. Here, we describe an atypical case of IgA-λ multiple myeloma, where double M-bands (one in β- and the other in γ-globulin region) were found during SPEP simulating biclonal gammopathy, although it was monoclonal in nature. This peculiar presentation of double M-bands in monoclonal gammopathy was attributed to polymeric forms of IgA by systematic workup. Further, we discuss how true and apparent biclonality can be distinguished by inexpensive analytical techniques in resource-constrained settings.



How to cite this article:
Bora K, Das U, Barman B, Ruram AA. Monoclonal gammopathy with double M-bands: An atypical presentation on serum protein electrophoresis simulating biclonal gammopathy.Indian J Pathol Microbiol 2017;60:590-592


How to cite this URL:
Bora K, Das U, Barman B, Ruram AA. Monoclonal gammopathy with double M-bands: An atypical presentation on serum protein electrophoresis simulating biclonal gammopathy. Indian J Pathol Microbiol [serial online] 2017 [cited 2019 Dec 7 ];60:590-592
Available from: http://www.ijpmonline.org/text.asp?2017/60/4/590/222970


Full Text



 Introduction



Monoclonal gammopathies are hematological disorders characterized by high levels of an immunologically homogeneous immunoglobulin (known as monoclonal protein or M-protein or paraprotein), produced by a rapidly and abnormally proliferating clone of B-lymphocytes and/or plasma cells.[1],[2] They are usually associated with multiple myeloma, monoclonal gammopathy of unknown significance, and Waldenstrom's macroglobulinemia though their presence in other pathologies, namely, cryoglobulinemia, primary amyloidosis, leukemias, lymphomas, etc., has also been described.[1],[2],[3]

The M-protein is amenable to detection by serum protein electrophoresis (SPEP) as a single discrete band (M-band), mostly in the γ-globulin region.[1],[3],[4],[5] However, it may sometimes occur in the β- or α-globulin regions instead, especially when the M-protein is of IgM or IgA isotype.[3],[4] Rarely, SPEP shows the simultaneous presence of two distinct M-bands (found in 3%–4% of multiple myeloma cases).[1],[3],[6] This condition is termed as “biclonal gammopathy” or “double gammopathy” – an outcome of simultaneous clonal expansions of two different neoplastic cell lines.[1],[3],[6] Recognizing biclonal gammopathies is of interest because assessing both the clonal proteins may help in evaluating the synchronicity of response of the two clones during treatment and follow-up.[1] Besides, double M-bands are frequently associated with other hematological malignancies (viz., leukemias and lymphomas).[6]

However, we report an atypical presentation of multiple myeloma which showed double M-bands in SPEP in the absence of true biclonality. We also describe how such situations may be distinguished through inexpensive analytical techniques.

 Case Report



A 69-year-old woman who underwent percutaneous transluminal coronary angioplasty (12 months ago) presented with fatigue and generalized weakness on follow-up in a medical college hospital from Meghalaya, northeast India. There was pallor on general examination. Clinical examination (of the abdomen, chest, cardiovascular and nervous systems) was unremarkable. Her electrocardiography and echocardiography were normal. Bone pain or sternal tenderness was absent.

Routine investigations detected anemia (Hb 83 g/L), leukocytosis (11,500 cells/mm3), and raised erythrocyte sedimentation rate (98 mm/1st h). Biochemical investigations of the serum revealed increased total protein (9.9 g/dL), diminished albumin (3.2 g/dL), and grossly reversed albumin/globulin ratio. Renal function tests (creatinine 1.1 mg/dL, urea 30 mg/dL) were normal while ionized calcium (1.6 mmol/L) was elevated mildly. Elevations in uric acid (8.2 mg/dL) and lactate dehydrogenase (956 IU/L) were also noted. Ultrasonography of the abdomen showed mild cortical thinning of both kidneys. No osteolytic lesions were found during radiological examination. The patient was admitted for further evaluation.

Bone marrow biopsy showed hypercellular marrow with 40% plasma cells. SPEP was performed in agarose gels (SAS-1 SP-24 kit) in an integrated electrophoresis system (SAS-1plus SAS-2, Helena Biosciences Europe, UK). The gel picture showed two separate M-bands (M1 and M2 in β- and γ-globulin regions, respectively, [Figure 1]a), producing two distinct M-spikes in the densitometry tracing [Figure 1]b. Thus, the possibility of biclonal gammopathy was considered. Alternatively, as one of the M-bands was present in the β-region, a monoclonal M-protein of IgM or IgA (known for tendency to aggregate) isotype producing a second M-band due to polymeric form was also suspected.{Figure 1}

Immunofixation electrophoresis (IFE) was desirable. However, since this facility was not available in Meghalaya, confirmation by IFE was sought in a distant referral diagnostic center. While awaiting the IFE report, we tried to narrow down our suspicion using a simple and inexpensive method of repeating SPEP under reducing conditions (pretreating 100 μL serum with 10 μL of β-mercaptoethanol). The M2-band detected previously in the γ-region was absent in the repeat gel-run. Instead, only a single intense and large M-band in the β-region appeared [Figure 1]c and [Figure 1]d. Therefore, true biclonal gammopathy was ruled out. This was further substantiated by the subsequent IFE report, which detected an IgA-λ monoclonal protein. Two bands were present at different positions that stained positive for only one heavy chain (IgA) and one light chain (lambda) [Figure 2]. In view of the above, the two M-bands in SPEP were attributed to polymeric forms of the same monoclonal protein. Raised serum levels of total IgA (56.5 g/L), lambda light chain (288 mg/L), and β-2-microglobulin (6198 ng/mL) were found on additional workup. The patient was diagnosed as IgA-λ multiple myeloma and started on chemotherapy (bortezomib, lenalidomide, and dexamethasone).{Figure 2}

 Discussion



Multiple myeloma is the second-most common hematological malignancy and accounts for nearly 2% of all cancer deaths.[2] SPEP constitutes an important part of the standard laboratory evaluation for M-protein.[1],[2],[3],[4],[5] However, because of unique biological and physicochemical properties, M-proteins of IgA variety may produce peculiar and atypical patterns during electrophoresis which may pose diagnostic difficulties, namely, more anodal migration (close to the β-region) due to lower isoelectric pH, apparent absence of light chains during IFE due to sequestration of light chain epitopes by the quaternary structure of IgA, and confounding by a fibrinogen band.[1],[3],[7]

In our case, two M-bands were observed in a multiple myeloma patient that raised the possibility of biclonal gammopathy. However, this was subsequently ruled out, and the double M-bands were attributed to polymeric forms of a single IgA M-protein. IgA paraproteins tend to aggregate and form polymers.[1],[3] Detecting IgA polymers in multiple myeloma is of clinical relevance because such patients are prone to hyperviscosity syndrome.[8] Further, polymeric IgA can cause anomalous laboratory findings (e.g., spurious hypercalcemia or overestimation of hemoglobin) that may lead to inappropriate treatment decisions.[9],[10] These polymers have a different mobility than the parent monomeric M-protein, thus yielding multiple bands at different positions on SPEP.[1],[3] IFE can be useful in such cases as it has good resolution and provides M-protein isotype information. However, IFE is expensive and still not widely available. Thus, SPEP continues to be the mainstay for M-protein evaluation in many resource-limited settings,[4],[5] like ours. In such situations, the inexpensive method of SPEP after pretreatment with reducing agents (such as β-mercaptoethanol and dithiothreitol) can distinguish true biclonality from polymeric forms.[3] These reductants depolymerize IgA polymers by disrupting disulfide bonds. Multiple bands from IgA polymers are reduced to a single M-spike while the spikes in true biclonal gammopathies are unaffected by this pretreatment, thus facilitating distinction.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Acknowledgment

We express our heartfelt gratitude to Prof. Probodh Borah, Mr. Naba Kumar Deka, and Md. Iftikar Hussain of State Biotech Hub, College of Veterinary Sciences, Khanapara, Guwahati (Assam), who kindly provided us with the β-mercaptoethanol (Catalog no. MB 041, HiMedia Laboratories, Mumbai, India) reagent at the shortest notice that enabled carrying out the repeat gel-run under reducing conditions. We are also thankful to Dr. Himangshu Mazumdar, Consultant Biochemist of Dr Lal PathLabs, Rohini, New Delhi for his valuable inputs.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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