Detecting M-Protein via Mass Spectrometry and Affinity Beads: Enrichment With Mixed Kappa-Lambda Beads Enables Prompt Application in Clinical Laboratories.

Background: Detecting monoclonal protein (M-protein), a hallmark of plasma cell disorders, traditionally relies on methods such as protein electrophoresis, immune-electrophoresis, and immunofixation electrophoresis (IFE). Mass spectrometry (MS)-based methods, such as matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and electrospray ionization-quadrupole time-of-flight (ESI-qTOF) MS, have emerged as sensitive methods. We explored the M-protein-detection efficacies of different MS techniques. Methods: To isolate immunoglobulin and light chain proteins, six types of beads (IgG, IgA, IgM, kappa, lambda, and mixed kappa and lambda) were used to prepare samples along with CaptureSelect nanobody affinity beads (NBs). After purification, both MALDI-TOF MS and liquid chromatography coupled with Synapt G2 ESI-qTOF high-resolution MS analysis were performed. We purified 25 normal and 25 abnormal IFE samples using NBs and MALDI-TOF MS (NB-MALDI-TOF). Results: Abnormal samples showed monoclonal peaks, whereas normal samples showed polyclonal peaks. The IgG and mixed kappa and lambda beads showed monoclonal peaks following the use of daratumumab (an IgG/kappa type of monoclonal antibody) with both MALDI-TOF and ESI-qTOF MS analysis. The limits of detection for MALDI-TOF MS and ESI-qTOF MS were established as 0.1 g/dL and 0.025 g/dL, respectively. NB-MALDI-TOF and IFE exhibited comparable sensitivity and specificity (92% and 92%, respectively). Conclusions: NBs for M-protein detection, particularly with mixed kappa-lambda beads, identified monoclonal peaks with both MALDI-TOF and ESI-qTOF analyses. Qualitative analysis using MALDI-TOF yielded results comparable with that of IFE. NB-MALDI-TOF might be used as an alternative method to replace conventional tests (such as IFE) to detect M-protein with high sensitivity.

Congophilic fibrils in the glomeruli with polyclonal immunoglobulin gamma staining - another cause for diagnostic overlap: A case report.

BACKGROUND: Glomerulopathy with fibrillary deposits is not uncommon in routine nephropathology practice, with amyloidosis and fibrillary glomerulonephritis being the two most frequently encountered entities. Renal amyloid heavy and light chain (AHL) is relatively uncommon and its biopsy diagnosis is usually limited to cases that show strong equivalent staining for a single immunoglobulin (Ig) heavy chain and a single light chain, further supported by mass spectrometry (MS) and serum studies for monoclonal protein. But polyclonal light chain staining can pose a challenge. CASE SUMMARY: Herein we present a challenging case of renal AHL with polyclonal and polytypic Ig gamma (IgG) staining pattern by immunofluorescence. The patient is a 62-year-old Caucasian male who presented to an outside institution with a serum creatinine of up to 8.1 mg/dL and nephrotic range proteinuria. Despite the finding of a polyclonal and polytypic staining pattern on immunofluorescence, ultrastructural study of the renal biopsy demonstrated the presence of fibrils with a mean diameter of 10 nm. Congo red was positive while DNAJB9 was negative. MS suggested a diagnosis of amyloid AHL type with IgG and lambda, but kappa light chains were also present supporting the immunofluorescence staining results. Serum immunofixation studies demonstrated IgG lambda monoclonal spike. The patient was started on chemotherapy. The chronic renal injury however was quite advanced and he ended up needing dialysis shortly after. CONCLUSION: Tissue diagnosis of AHL amyloid can be tricky. Thorough confirmation using other available diagnostic techniques is recommended in such cases.

A Case Report: Monoclonal Gammopathy of Undetermined Significance Presenting With Renal Amyloidosis and Reactive Thrombocytosis.

Monoclonal gammopathy of undetermined significance (MGUS) is a pre-neoplastic condition involving plasma cells or lymphoplasmacytic proliferation-clinical presentations ranging from asymptomatic to symptoms of systematic organ involvement. It is commonly associated with light chain amyloidosis and usually strengthens during diagnosis. It is usually associated with thrombocytopenia in addition to anemia. This case report focuses on a 63-year-old Hispanic female who initially presented without any symptoms but with severe thrombocytosis. The finding of renal amyloidosis boosts the final diagnosis of MGUS. Rarely a patient is initially presented with severe thrombocytosis despite thrombocytopenia, which is commonly associated with plasma cell disorders. The case emphasizes the need for considering plasma cell disorders in patients with abnormal hematologic manifestations. It highlights the importance of timely identification and intervention to prevent irreversible organ damage by providing a detailed analysis of the clinical presentation and diagnostic evaluation.

Prevalence of monoclonal gammopathy of undetermined significance in Shenzhen, China.

BACKGROUND: Data on the prevalence of monoclonal gammopathy of undetermined significance (MGUS) in China are very limited. Our aim was to determine the prevalence and clinical characteristics of MGUS in a large Chinese population. METHODS: This study included 49,220 healthy people who received serum immunofixation electrophoresis (sIFE) and serum protein electrophoresis (SPE) tests. Serum free light chain ratio, immunoglobulin quantification, and other clinically correlates of MGUS were performed for all patients with M-protein. RESULTS: A total of 576 MGUS patients were identified by sIFE, with a median age of 58 years and an overall prevalence of 1.17% (95% CI, 1.08-1.27). Among those aged 50 years and older, the prevalence of MGUS was 2.26% (95% CI, 2.04-2.50). The prevalence of MGUS was significantly higher in males than in females (P < 0.05). The median concentration of M-protein was 3.1 g/L, ranging from 0.5 g/L to 25.1 g/L. The M-protein type was IgG in 55.4% of MGUS patients, followed by IgA (31.1%), IgM (9.5%), IgD (0.5%), biclonal (2.3%), and light chain (1.2%). Abnormalities in SPE, FLC ratios, and immunoglobulin levels were observed in 78.3%, 31.1%, and 38.4% of MGUS patients, respectively. CONCLUSIONS: The prevalence of MGUS is substantially lower in southern China than in whites and blacks.

A case report of biclonal immunoglobulin D lambda/lambda multiple myeloma in patient with liver echinococcosis.

Less than 2% of all symptomatic multiple myeloma (MM) has immunoglobulin D (IgD) as monoclonal protein. Biclonal gammopathy is much rarer. At the time of diagnosis, disease is often in advanced stage, including renal failure, anemia, hypercalcemia and lytic bone lesions. Due to the rarity of myeloma itself, but also due to the fact that anti-IgD antisera is not used in routine practice, there are only a few reports of IgD MM described in the literature. This case report describes a patient with IgD lambda MM with anemia and renal failure. Anemia, renal failure, and > 80 percent plasma cells in bone biopsy in our patient with IgD lambda MM meets International Myeloma Working Group criteria for diagnosis of MM. The patient clinical course was similar to other patients with IgD MM. The final result of serum protein immunofixation (s-IFE) showed IgD lambda and free lambda monoclonal bands. To prevent misdiagnosis, it is necessary to use anti-IgD and anti-IgE antisera whenever the serum protein immunofixation with IgA, IgM, IgG, kappa and lambda antiserums shows a kappa or lambda monoclonal band without monoclonal band in heavy chain.

Monoclonal Gammopathy of Renal Significance (MGRS) - Case Series from a Tertiary Center in Kerala.

Monoclonal gammopathy of renal significance (MGRS) has gained importance because identifying the monoclonal deposit and addressing it, rather than treating renal dysfunction as the primary pathology, has salvaged the patients from progressing into end-stage renal disease. Since it affects elderly population, there could be a propensity to misdiagnose them with cardiorenal syndrome. We present four patients of MGRS diagnosed from our center. They presented with proteinuria or unexplained renal dysfunction. Three of the patients were diagnosed to have amyloidosis, of which two had lambda-type and one had kappa amyloidosis. The fourth patient had fibrillary glomerulonephritis with kappa restriction, further evaluation of which led to diagnosis of chronic lymphocytic leukemia. Absence of "M" band in protein electrophoresis and a normal bone marrow study should not stop physicians from further evaluation. Quantitative serum immunofixation electrophoresis and electron microscopic examination of renal biopsy have become a comprehensive diagnostic tool in such patients.

Characteristics of isatuximab-derived interference in serum protein electrophoresis and immunofixation, and an absence of sustained in vivo interference due to belantamab mafodotin and denosumab.

OBJECTIVES: Some therapeutic monoclonal antibodies, like daratumumab and elotuzumab, produce interfering monoclonal bands on serum protein electrophoresis (SPEP) and immunofixation electrophoresis (IFE). Whether other common therapeutic antibodies also produce interference has not been systematically evaluated. DESIGN AND METHODS: SPEP/IFE from patients receiving isatuximab (48 patients), belantamab mafodotin (BM; 41), and denosumab (41) were retrospectively reviewed for therapeutic antibody interference. Cases exhibiting isatuximab interference were quantified and the maximum duration of isatuximab effect was evaluated. To characterize band position, neat human serum was spiked with BM or denosumab at supratherapeutic concentrations. Band migration patterns were compared on SPEP and IFE, with band position expressed relative to other constant protein fractions. RESULTS: Isatuximab-induced IFE interference was common (81.3 % of evaluated patients) with a maximum observed duration of 8 weeks. 10.4 % of isatuximab patients had IgG kappa monoclonal gammopathies that co-migrated with the drug; this subset could benefit from HYDRASHIFT 2/4 isatuximab testing. 8.3 % of IFE cases were negative for an isatuximab band but showed large, endogenous M-spikes migrating elsewhere. All patients in this group expired within 1 year of this finding. We hypothesize that an inability to detect isatuximab in this setting corresponds to a large residual myeloma burden that reduces isatuximab serum concentration. This observation may serve as a negative prognostic factor. Spiking studies demonstrated that BM and denosumab produce interference in vitro, but sustained interference was not observed in >40 treated patients. CONCLUSIONS: Therapeutic antibody interference in patients receiving isatuximab is common, and can persist for at least 8 weeks after administration. >10 % of patients receiving isatuximab may benefit from HYDRASHIFT testing post-therapy. In contrast, BM and denosumab fail to produce sustained interference in treated patients.

Multiple Myeloma: A Rare Presentation As Unilateral Pleural Effusion.

Multiple myeloma (MM) is a hematologic malignancy characterized by the clonal proliferation of plasma cells in the bone marrow. It commonly presents with bone pain, anemia, renal failure, and hypercalcemia. Pleural effusion in MM usually has multiple causes, but it is rare for the effusion to be due to myelomatous deposition of the pleura. Here, we present a rare case in which the patient presented to the outpatient department with a dry cough, breathlessness, and generalized weakness. The patient was diagnosed with MM with myelomatous pleural effusion (MPE), highlighting the importance of considering MM as a differential diagnosis in patients with atypical presentations. MPE indicates a poor prognosis, and early consideration of MPE can lead to an earlier diagnosis and a more effective treatment of MM.

Performance Characteristics and Limitations of the Available Assays for the Detection and Quantitation of Monoclonal Free Light Chains and New Emerging Methodologies.

Light chain measurements form an essential component of the testing strategy for the detection and monitoring of patients with suspected and/or proven plasma cell disorders. Urine-based electrophoretic assays remain at the centre of the international guidelines for response assessment but the supplementary role of serum-free light chain (FLC) assays in response assessment and the detection of disease progression due to their increased sensitivity has been increasingly recognised since their introduction in 2001. Serum FLC assays have also been shown to be prognostic across the spectrum of plasma cell disorders and are now incorporated into risk stratification scores for patients with monoclonal gammopathy of undetermined significance (MGUS), smouldering multiple myeloma, and light chain amyloidosis (AL amyloidosis), as well as being incorporated into the criteria for defining symptomatic multiple myeloma. There are now multiple different commercially available serum FLC assays available with differing performance characteristics, which are discussed in this review, along with the implications of these for patient monitoring. Finally, newer methodologies for the identification and characterisation of monoclonal FLC, including modifications to electrophoretic techniques, mass spectrometry-based assays and Amylite, are also described along with the relevant published data available regarding the performance of each assay.

Oligoclonal gammopathy: An analysis of 253 cases.

BACKGROUND: Oligoclonal gammopathy (OG) is a rare disorder of the lymphoid system that is characterized by the presence of at least 2 distinct monoclonal proteins in a patient's serum or urine. The biological and clinical characteristics of this disease are as yet poorly understood. OBJECTIVES: The study aimed to assess whether there are significant differences between patients with OG regarding the developmental history (i.e., OG diagnosed at the first presentation compared to OG that has developed in patients with an original monoclonal gammopathy) and the number of monoclonal proteins (2 compared to 3). Moreover, we attempted to determine when secondary oligoclonality develops following the original diagnosis of monoclonal gammopathy. MATERIAL AND METHODS: Patients were analyzed with regard to their age at diagnosis, sex, serum monoclonal proteins, and underlying hematological disorders. Multiple myeloma (MM) patients were additionally evaluated for their Durie-Salmon stage and cytogenetic alterations. RESULTS: Patients with triclonal gammopathy (TG: n = 29) did not differ significantly from patients with biclonal gammopathy (BG: n = 223) (p = 0.81) in terms of age at diagnosis and the dominant diagnosis (MM was the most common diagnosis (65.0% and 64.7%, respectively)). In both cohorts, myeloma patients were mainly classified to the Durie-Salmon stage III. In the TG cohort, there was a higher proportion of males (69.0%) than among patients with BG (52.5%). Oligoclonality developed at various times after diagnosis (up to 80 months in the investigated cohort). However, the occurrence of new cases was higher during the initial 30-month period following the diagnosis of monoclonal gammopathy. CONCLUSIONS: There are only small differences between patients with primary compared to secondary OG, between BG and TG, and most patients have a combination of IgGκ+IgGλ. Oligoclonality could develop at any time after the diagnosis of monoclonal gammopathy, but it happens more frequently during the first 30 months, with advanced myeloma being the most prevalent underlying disorder.

Isoelectric focusing followed by affinity immunoblotting to detect monoclonal free light chains in monoclonal gammopathies: Comparison with immunofixation electrophoresis and free light chain ratio.

BACKGROUND: Isoelectric focusing (IEF) is a method with an exquisite resolution, and coupled with affinity immunoblotting (AIB), it can provide superior sensitivity to detect monoclonal free light chains (FLC). METHODS: We tested the hypothesis that IEF/AIB is more sensitive and specific for monoclonal FLC detection in serum and urine samples than conventional methods, that is, electrophoresis (ELP), immunofixation (IF) and serum FLC ratio assessment. Investigation included 107 samples of 68 patients, among which 21 multiple myeloma patients were recently tested for minimal residual disease and 18 patients with AL amyloidosis. RESULTS: Monoclonal FLC were detected by IEF/AIB in 37% of serum samples negative for monoclonal FLC on ELP/IF. As for urine samples, significant advantage of the IEF/AIB over ELP/IF was not demonstrated. Considering both serum and urine results, IEF/AIB definitely revealed monoclonal FLC in 20/83 (24%) of ELP/IF-negative samples. FLC ratio was abnormally high (>1.65) in all 11 patients definitely positive for monoclonal FLC kappa by IEF/AIB but also in 16/47 (34%) IEF/AIB-negative samples. Abnormally low values (<0.26) were found only in 10/28 samples (36%) positive for monoclonal FLC lambda. Appropriate use of renal FLC ratio reference range reduced the number of presumably false positives (6/47, i.e. 13%) but not false negatives (17/28, i.e. 61%). CONCLUSIONS: The IEF/AIB method is more sensitive than IF and might be used in patients with negative IF results before deciding whether to proceed to minimal residual disease testing.

Prognostic significance of serum monoclonal proteins based on immunofixation electrophoresis in B-cell non-Hodgkin lymphoma.

The presence of serum monoclonal components has been associated with poor outcomes in various hematological malignancies. The current study focused on exploring its prognostic role in B-cell non-Hodgkin lymphoma. Our study represented 314 patients with information on serum immunofixation electrophoresis at diagnosis that were available with B-cell non-Hodgkin lymphoma. IFE was positive in 61 patients (19%). Baseline features were comparable between pairs of groups, poor ECOG PS, B symptoms, advanced stage, and high-risk IPI score were significantly more frequent in the + IFE group. Shorter PFS and OS of B-NHL patients were observed in patients who presented at diagnosis with a + IFE, and IFE was the independent predictor of PFS and OS in multivariate analysis. Moreover, integrating IFE into the IPI-M1, IPI-M2, and IPI-M3 models improved the area under the curve for more accurate survival prediction and prognosis. Serum monoclonal proteins are significant prognostic indicators for newly diagnosed B-cell non-Hodgkin lymphoma that can early identify patients with poor prognosis and guide clinical treatment decisions.

Urine immunofixation electrophoresis and serum free light chain analyses benefit diagnosis of multiple myeloma in orthopedic patients with normal serum total proteins, creatinine, calcium, and hemoglobin.

BACKGROUND: A substantial number of patients with multiple myeloma (MM) who have bone destruction are initially admitted into the orthopedic service at the hospital. However, routine laboratory testing usually fails to identify these patients, thus delaying optimal therapy. Therefore, there is a clear medical need for early diagnosis of MM in these patients. METHODS: Between 2019 and 2021, 42 patients receiving treatment for orthopedic conditions had normal hemoglobin (Hb), total protein (TP), albumin (ALB), creatinine (CREA), and blood calcium (Ca) levels before their surgical procedure(s) but were subsequently pathologically confirmed to have MM, based on their presenting orthopedic symptoms. During the same period, 52 patients with orthopedic conditions were pathologically excluded from the diagnosis of MM and were recruited into our control group. Serum free light chain (sFLC) testing was performed in 94 consecutive patients in the orthopedic service using Siemens N Latex FLC kits. The levels of Hb, TP, ALB, CREA, and Ca were also measured. All 42 patients with MM were divided into group A (n = 25: κ proliferation) and group B (n = 17: λ proliferation) by the pathology department. RESULTS: There were no significant differences in levels of Hb, TP, ALB, CREA, and Ca between group A and group B and the control group. However, the sFLC κ/λ ratio of group A and B was also significantly different from that of the control group (P < .001). The results of serum immunofixation electrophoresis (IFE) testing demonstrated negative results in 14 cases (58.3%) in group A and 4 cases (25.0%) in group B. CONCLUSIONS: Some patients with orthopedic conditions who do not have typical MM laboratory results, such as those with abnormal Hb, TP, ALB, CREA, and Ca levels before their operation(s), actually have MM. MM should be highly suspected in patients with unexplained bone lesions and with an abnormal sFLC κ/λ ratio. Further tissue or bone marrow biopsy is needed in these patients even if serum and urine IFE results are negative and light chain ratio is normal.

Understanding the Constraints and Optimization of Serum Immunofixation Electrophoresis and Serum Free Light Chains for Detecting Monoclonal Proteins: A Single-Center Experience.

Introduction Serum immunofixation electrophoresis (SIFE) and serum free light chain (SFLC) assay are imperative investigations in diagnosis and follow-up of multiple myeloma (MM). SFLC assays are reported to have higher sensitivity than SIFE. However, discrepancies have been reported between them. The current study was aimed at assessing concordance and discordance between SIFE and SFLC results in MM. Methods A total of 450 observations of both SIFE and SFLC were obtained from treatment-naive and follow-up MM patients. Results One hundred and twenty-nine (28.7%) values were observed as discordant, that is, positive SIFE with normal SFLC ratio or negative SIFE with abnormal SFLC ratio ( p -value < 0.00001). Proportion of discordance was higher in SIFE positive-SFLC normal cases than SIFE negative-SFLC abnormal cases. Discordance was more frequent in follow-up cases. Conclusion Negative SFLC alone may not be reliable for MM follow-up. Algorithm may be based on SFLC measurements on each follow-up till attainment of normal SFLC ratio. Once SFLC normalizes, follow-up may be done with SIFE. If SIFE is positive, further follow-up with SIFE may be initiated.

Evusheld, a SARS-CoV-2 spike protein-directed attachment inhibitor, appears in serum protein electrophoresis and immunofixation: a case study.

Serum protein electrophoresis (SPE) and immunofixation (IFE) assays are commonly used to diagnose and monitor patients with multiple myeloma (MM). Identifying analytical interferences in SPE and IFE caused by therapeutic monoclonal antibodies (tmAbs) can be challenging. Here we report the case of a 72-year-old male with a long history of relapsed immunoglobulin (Ig)G kappa MM. A follow-up SPE showed the original peak plus 2 additional cathode peaks. Immunofixation was ordered as a reflex test to investigate the new peaks that showed initial patient monoclonal IgG kappa in addition to 2 restricted bands of the IgG kappa type. Therapeutic monoclonal antibody interference was suspected and the patient's chart was reviewed. The patient was not on any antimyeloma monoclonal antibody therapy. However, preexposure prophylaxis therapeutic monoclonal antibodies tixagevimab plus cilgavimab (Evusheld) for severe acute SARS-CoV-2 was administered approximately 45 minutes before sample collection, which led to the identifiable spikes and correlated bands. After 2 days, the IgG kappa bands disappeared, confirming this therapy's effect on SPE and IFE. Therefore, clinical pathologists should be aware of when providers prescribe new monoclonal antibody therapy and become familiar with the position of commonly prescribed (tmAbs) therapies at their institutions.

Exceptional Manifestation of Multiple Myeloma.

Despite being a rare occurrence, multiple myeloma (MM) has been reported as an alternative cause of pleurisy, with approximately 50 documented cases in the literature so far. In this case report, we present the clinical scenario of a patient who sought medical attention due to symptoms of dyspnea, chest pain, and weight loss. Through a comprehensive diagnostic evaluation, it was determined that the patient's pleural involvement was attributable to MM, a hematological malignancy. This case highlights the importance of considering MM as a potential etiology in patients presenting with pleural manifestations, even in settings where tuberculosis is the prevailing cause.

Identifying therapeutic monoclonal antibodies using target protein collision electrophoresis reflex assay to separate the wheat from the chaff.

Monoclonal gammopathies are characterized by the presence of monoclonal immunoglobulins, also known as M-proteins. Therapeutic monoclonal antibodies (t-mAbs) can interfere in laboratory assays used to monitor the state of disease, such as serum protein electrophoresis (SPE) and immunofixation electrophoresis (IFE). To establish a correct interpretation of IFE, Target protein-Collision Immunofixation Electrophoresis Reflex Assay (T-CIERA) was developed to identify t-mAbs in IFE. Here we demonstrate that T-CIERA is applicable to a wide variety of t-mAbs for which the target protein is commercially available. Moreover, the shift observed was characteristic for each t-mAb, and T-CIERA enabled the identification of multiple t-mAbs sharing a common target protein. Additionally, the lower limit of detection (LLOD) was determined objectively, and T-CIERA demonstrated an adequate LLOD for all tested t-mAbs. Furthermore, T-CIERA was also successfully applied to serum samples obtained from patients receiving daratumumab, isatuximab, elotuzumab, and durvalumab treatment. In conclusion, T-CIERA is a suitable reflex assay for identifying a wide variety of t-mAbs, including those for which no commercial assay is available to deal with their interference. Moreover, CD38-CIERA could serve as an alternative or complementary test to the commercially available Hydrashift assay kits. T-CIERA would enable laboratories without mass spectrometry equipment and expertise in this area to distinguish between drug and disease to improve clinical response monitoring and diagnosis of monoclonal gammopathies.

Recommendations for the study of monoclonal gammopathies in the clinical laboratory. A consensus of the Spanish Society of Laboratory Medicine and the Spanish Society of Hematology and Hemotherapy. Part I: Update on laboratory tests for the study of monoclonal gammopathies.

Monoclonal gammopathies (MG) are characterized by the proliferation of plasma cells that produce identical abnormal immunoglobulins (intact or some of their subunits). This abnormal immunoglobulin component is called monoclonal protein (M-protein), and is considered a biomarker of proliferative activity. The identification, characterization and measurement of M-protein is essential for the management of MG. We conducted a systematic review of the different tests and measurement methods used in the clinical laboratory for the study of M-protein in serum and urine, the biochemistry and hematology tests necessary for clinical evaluation, and studies in bone marrow, peripheral blood and other tissues. This review included literature published between 2009 and 2022. The paper discusses the main methodological characteristics and limitations, as well as the purpose and clinical value of the different tests used in the diagnosis, prognosis, monitoring and assessment of treatment response in MG. Included are methods for the study of M-protein, namely electrophoresis, measurement of immunoglobulin levels, serum free light chains, immunoglobulin heavy chain/light chain pairs, and mass spectrometry, and for the bone marrow examination, morphological analysis, cytogenetics, molecular techniques, and multiparameter flow cytometry.

Multiple myeloma presenting as blepharitis in a horse.

Myeloma-related disorders, including multiple myeloma, extramedullary plasmacytoma, and solid osseous plasmacytoma, are rare in horses. Clinical complaints for myeloma-related disorders are nonspecific, and when present, M-protein location is more variable on protein electrophoresis in horses relative to dogs and cats. Here, we describe a case of a 15-year-old Thoroughbred mare who presented with recurrent blepharitis. Marked hyperglobulinemia was an incidental finding on routine hematologic and biochemical testing. Bone marrow aspiration consisted of >30% plasma cells, and serum protein electrophoresis demonstrated a monoclonal gammopathy in the alpha 2 fraction leading to a diagnosis of multiple myeloma. Immunofixation and radial immunodiffusion confirmed the presence of an IgG M-protein. Based on a restricted peak in the alpha 2 location, the specific M-protein is suspected to be IgG(T), an IgG isotype unique to horses. M-protein migration in horses is variable relative to dogs and cats, yet immunofixation can still be used to identify equine IgG M-protein isotypes. The unique clinical presentation in this case also serves as a reminder to consider neoplasia in horses with unusual or nonspecific clinical signs.

Waldenström's Macroglobulinemia in a Normoproteinemic Dog with Atypical Bimorphic Plasmacytoid Differentiation and Monoclonal Gammopathy.

A 2-year-old neutered female Small Munsterlander dog was presented for an insect bite. Physical examination revealed a poor body condition, a peripheral lymphadenomegaly, and suspected splenomegaly. A complete blood count (Sysmex XN-V) revealed marked leukocytosis with lymphocytosis and abnormal dot plots. An abnormal monomorphic lymphoid population and marked rouleaux formation were noted on the blood smear. Lymph node aspirates contained an atypical bimorphic population of lymphocytes, either with a plasmacytoid or a blastic appearance. This double population was also found in the spleen, liver, bone marrow, tonsils, and other tissues. Peripheral blood and lymph node clonality assays revealed clonal BCR gene rearrangement. Flow cytometry revealed a mixed population of small-sized B-cells (CD79a+ CD21+ MHCII+) and medium-sized B-cells (CD79a+ CD21- MHCII-) in lymph nodes and a dominant population of small-sized mature B-cells (CD21+ MHCII+) in peripheral blood. Though normoproteinemic, serum protein electrophoresis revealed an increased α2-globulin fraction with an atypical restricted peak, identified as monoclonal IgM by immunofixation. Urine protein immunofixation revealed a Bence-Jones proteinuria. A diagnosis of Waldenström's macroglobulinemia was made. Chemotherapy was initiated, but the dog was euthanized 12 months after the initial presentation due to marked clinical degradation.