Serum viscosity and hyperviscosity syndrome in IgG multiple myeloma. Report on 10 patients and a review of the literature

[Serum hyperviscosity syndrome: Update 2024]

Seric hyperviscosity syndrome is a medical emergency linked to hyperproteinemia. The clinical diagnosis hinges on a triad of symptoms: mucosal hemorrhages, visual disturbances, and neurological disorders, observed in the most severe cases. Diagnosis is swiftly confirmed through an urgent fundoscopic examination. Therapeutic plasma exchange is the primary treatment for severe cases or following confirmation by fundoscopy. Laboratory tests predominantly identify the syndrome's etiology, with Waldenström's macroglobulinemia (characterized by a marked IgM peak) being the most common cause, followed by multiple myeloma and cryoglobulinemias. To prevent recurrence, targeted treatment of the underlying cause is implemented following plasma exchange sessions.

A Case of IgG1-Lambda Multiple Myeloma With Hyperviscosity Syndrome and Cryoglobulinemia: Identification of the Subclass Fraction by Immunoelectrophoresis and Immunofixation Electrophoresis

Hyperviscosity syndrome (HVS) is a complication of monoclonal plasma cell tumors. The frequency of HVS depends on the type of monoclonal protein. Immunoglobulin M (IgM) is more closely associated with HVS than IgG, and among IgG subclass monoclonal proteins, IgG3 is most frequently associated with HVS. We herein report a 44-year-old woman with multiple myeloma (MM), HVS, and cryoglobulinemia. Her monoclonal protein and cryoglobulin were IgG1-lambda (λ). She developed HVS at a lower monoclonal protein level because of the properties of the IgG1-derived monoclonal protein and cryoglobulin. Our case highlights the fact that identifying the IgG subclass is useful in predicting the risk of complicating HVS.

Necrotizing Enterocolitis in a Patient With Newly Diagnosed Multiple Myeloma and Hyperviscosity Syndrome: A Case Report

Multiple myeloma (MM) is a clonal plasma cell proliferative disorder characterized by the abnormal increase of monoclonal paraprotein and can lead to specific end-organ damage. Necrotizing enterocolitis or bowel necrosis is a surgical emergency defined by cellular death because of reduced blood flow to the gastrointestinal tract. We report a case of a 75-year-old female who was diagnosed with hyperviscosity syndrome (HVS) and was sent to ED. Further workup showed that she had a new diagnosis of IgG kappa MM for which she was started on chemotherapy. Later, she developed respiratory distress and abdomen distention with less frequent bowel movements, and general surgery was consulted. CT scan of the abdomen and pelvis with contrast showed findings consistent with bowel ischemia vs infarction. The patient was immediately taken to the operating room, and exploratory laparotomy showed nonsurvivable bowel necrosis. She was transitioned to comfort care and passed away later. We aim to increase awareness among physicians to include HVS as one of the possible complications of MM and to detect it early to prevent morbidity and mortality.

Prognosis of hyperviscosity syndrome in newly diagnosed multiple myeloma in modern-era therapy: A real-life study

Hyperviscosity syndrome (HVS) is a rare complication of newly diagnosed multiple myeloma (NDMM) related to high tumour burden. Studies about the prognosis of HVS in modern-era therapy for NDMM are missing. We investigated a retrospective cohort study of NDMM with HVS between 2011-2021. Thirty-nine NDMM patients with HVS were included. HVS presentation was heterogeneous, with asymptomatic, mild, and neurological forms in 23%, 59%, and 18% of cases, respectively. No thrombosis or major bleeding was observed. Therapeutic plasma exchanges were used in 92% of patients, which were effective and well tolerated. No rebound effect was observed. All patients except one had at least one CRAB criterion. Most of the patients received bortezomib and high-dose steroids (95%) associated with an immunomodulatory drug (43%) or alkylating agents (42%). HVS in NDMM patients had dismal overall survival matched to multiple myeloma patient controls (without HVS) in our center (median: 3.6 vs. 7.7 years, p=0.01), as confirmed by multivariate analysis. Early deaths (in the first two months) occurred in 21% of older patients (>65 years). HVS in NDMM patients is a rare but life-threatening complication associated with high lethality in older patients and be a potential dismal prognosis factor in the modern treatment era.

Myeloma light chain cast nephropathy, a review

Multiple Myeloma is a plasma cell proliferative disorder that commonly involves the kidney. Renal impairment is a serious complication during the course of the disease that is associated with increased morbidity and mortality. Light chain cast nephropathy is the predominant pattern of renal injury in Multiple Myeloma. This review article focuses on the pathophysiology and diagnostic approach of myeloma cast nephropathy. The management of precipitating factors as well as anti-plasma cell treatment modalities in the context of renal impairment are also discussed.

Cerebral infarction in IgG multiple myeloma with hyperviscosity

Cerebral infarction is an uncommon complication in multiple myeloma with hyperviscosity. Serum hyperviscosity may cause a variety of clinical manifestations including bleeding from mucosal membranes, congestive heart failure, retinopathy, and various neurologic deficits. These manifestations have been attributed to the presence of large quantities of asymmetrical molecules of high molecular weight in the serum. We recently experienced a case of multiple myeloma with acute cerebral infarction, which caused by hyperviscosity, as an initial manifestation in IgG multiple myeloma, and reviewed the relevant literature of myeloma presenting with the stroke. A 68-yr-old woman abruptly developed hypesthesia and monoplegia in the left leg. The stroke confirmed by the brain MRI and MR angiography, which revealed acute infarction at the right anterior cerebral artery territory. On admission, routine blood tests showed a slight decrease in hemoglobin and a marked increase in erythrocyte sedimentation rate. Peripheral blood smear, serum protein electrophoresis, serum visocity, and bone marrow aspiration showed that she had IgG multiple myeloma with hyperviscosity. She was treated by chemotherapy with cyclophosphamide and discharged with the improved clinical condition.

Neurologic Complications of Plasma Cell Disorders

Plasma cell disorders are associated with a wide spectrum of neurologic complications that predominantly involve the peripheral nervous system. Distinct clinical syndromes have been recognized, and antibodies to several glycoproteins of the peripheral nervous system have been identified. The main clinical, laboratory, immunologic, and pathologic features of neurologic complications that occur in patients with monoclonal gammopathies of unknown significance, multiple myeloma, plasmacytoma, plasma cell leukemia, Waldenstrom's macroglobulinemia, and immunoglobulin-related amyloidosis are summarized in this review. Knowledge of the pathogenesis in this group of disorders has increased in recent years, allowing better diagnosis and treatment.

Hyperviscosity syndrome

Hyperviscosity syndrome is clinically manifested by oronasal bleeding, retinal hemorrhages, and variable neurological symptoms. It occurs when resistance to flow of blood increases sharply, resulting in impaired transit through the microcirculatory system. The most common cause of hyperviscosity is increased concentrations of gamma globulins, either monoclonal in malignant disease or polyclonal, usually seen with rheumatic disorders. Increased numbers of red blood cells, as in polycythemia vera, can result in viscous blood. Extreme increases in concentrations of mature and immature white blood cells can also produce hyperviscosity. Treatment with plasma exchange is required when the clinical syndrome is symptomatic. Although plasma exchange is not a completely benign procedure, it represents the most effective method of controlling hyperviscosity.

Prevalence and clinical characteristics of a high cardiac output state in patients with multiple myeloma

PURPOSE

This study was undertaken to define the prevalence and clinical characteristics of patients with a high cardiac output state associated with multiple myeloma.

PATIENTS AND METHODS

Specifically, we evaluated clinical, laboratory, and two-dimensional and Doppler echocardiographic data in 36 patients with multiple myeloma. Cardiac output was determined noninvasively by a pulsed Doppler technique.

RESULTS

A high cardiac output state, defined as a cardiac index greater than or equal to 4.0 L/minute/m2, was present in eight of 34 (23.5%) subjects in whom cardiac output was measurable. None of the known causes of high output states could be identified in these patients. Four patients developed high output congestive heart failure, two of whom died. Age, sex, degree of anemia, serum calcium level, immunoglobulin type, or disease stage did not differ significantly between subjects with or without high output states. However, severe bone involvement was significantly more frequent in those patients with high cardiac output states, occurring in all eight patients with high cardiac indexes compared with nine of 26 patients with low or normal cardiac indexes (p = 0.001).

CONCLUSION

These data demonstrate that high cardiac output states are relatively common in patients with multiple myeloma and are associated with the presence of extensive bone disease.

Human immunoglobulin G and immunoglobulin G subclasses: biochemical, genetic, and clinical aspects

Human IgG consists of two identical heavy (H) chains and two identical light (L) chains joined by interchain disulfide bridges. Heterogeneity in the amino acid sequences of the H and L polypeptides results in at least three types of IgG variants at the structural and genetic levels. The four isotypic forms are IgG1, IgG2, IgG3, and IgG4, which share extensive homologies in the primary structure of their H chains. As a result, the subclasses cross-react antigenically, but they can be differentiated on the basis of subtle architectural dissimilarities. The biological and effector properties of the IgG isotypes have been associated, in part, with their structural differences. Genes determining the synthesis of human IgG heavy chains are located on chromosome 14. In several clinical situations the isotypes appear to be regulated or expressed in patterns reflecting the gene arrangement. The numeric designations of the subclasses correspond to the order of their proportional amounts in healthy adult serum: IgG1 greater than IgG2 greater than IgG3 greater than IgG4. Awareness of the importance of the roles of the four IgG isotypes in human health has steadily increased since they were first described in the 1960s. The recognition that deficits or increases in selected IgG subclasses may have clinical consequences has prompted considerable interest in quantifying the four isotypes in clinical specimens. In particular, deficiencies of IgG2, IgG3, and IgG4, singly or combined, are associated with chronic infections which may not be readily recognized in otherwise healthy people with normal serum total IgG concentrations. Different assay methods using polyclonal or monoclonal antisera with various calibrants have been applied; however, no standardized method exists at the present. IgG deficits are associated with gene defects and are acquired in secondary immunodeficiencies in conjunction with other disorders. IgG isotype selectivity has been recognized in autoimmune diseases and in response to carbohydrate and protein antigens derived from pathogenic microorganisms and common allergens.

Plasma cell dyscrasias: current status

This is a review of the current status of the monoclonal gammopathies (plasma cell dyscrasias). We begin with the recognition of a monoclonal protein in serum and urine. We briefly discuss the differential diagnosis of the monoclonal gammopathies. Clinical and laboratory findings as well as the management of multiple myeloma are addressed. Future approaches for the treatment of myeloma are provided. The variant forms of multiple myeloma, including smoldering myeloma, plasma cell leukemia, nonsecretory myeloma, IgD myeloma, osteosclerotic myeloma, solitary plasmacytoma of bone, and extramedullary plasmacytoma, are briefly reviewed. Diagnosis and treatment of Waldenström's macroglobulinemia are presented. The recognition and differential diagnosis of the heavy-chain diseases (gamma, alpha, and mu) are included. Monoclonal gammopathy of undetermined significance ("benign" monoclonal gammopathy) is presented in detail. Amyloidosis is not included in this review.

Light chain disease associated with the hyperviscosity syndrome

The hyperviscosity syndrome refers to a group of symptoms and signs related to increased blood viscosity often produced by monoclonal immunoglobulins. It is most frequently associated with Waldenström's macroglobulinemia and, on occasion, with other immunoglobulins that are capable of forming highly polymerized molecules. This article is a report on the first case of pure light chain myeloma associated with the hyperviscosity syndrome. The hyperviscous plasma in this case is secondary to the unusual degree of aggregation of kappa light chain as demonstrated by high-resolution electrophoresis, serum immunofixation, and Sephadex g-200 (Pharmacia, Piscataway, NJ) column chromatography.

Rheology of paraproteinaemias and the plasma hyperviscosity syndrome

The proper understanding of the causes, pathophysiology, diagnosis and management of the plasma hyperviscosity syndrome is based on good knowledge of malignant paraproteinaemias, properties of immunoglobulins, rheology of blood in the microcirculation, and modern plasma separation techniques. This multifaceted syndrome complicates less than ten per cent of IgA and IgG myelomas, and up to one-third of Waldenström's macroglobulinaemias. A few cases of HVS have also been reported in association with polyclonal hypergammaglobulinaemias. Excessive paraproteinaemia may cause the plasma HVS, especially when paraproteins are extraordinarily large, asymmetrical or cryosensitive, or if they aggregate into hyperviscous macroaggregates. The resultant severe microcirculatory impairment is mainly due to the combined effects of plasma hyperviscosity, significant plasma volume expansion and intense red cell aggregation. The individually variable general symptoms, bleeding tendency, ocular, neurological, cardiovascular, and renal manifestations and laboratory parameters of the HVS are summarized briefly. The majority of patients present hyperviscosity manifestations when the plasma viscosity exceeds 5-6 mPa.s. Plasmapheresis or plasma exchange have established themselves as efficient and safe modes of therapy of hyperviscosity and hypervolaemia. The therapeutic guidelines for the plasma HVS are briefly discussed with regard to recent experience with developing plasma separation techniques. Diagnostic and therapeutic advances combined with increasing haemorheological knowledge have greatly improved the proper management of this potentially lethal complication of paraproteinaemias.

Regulation of cerebral blood flow in response to changes in blood viscosity

Cerebral blood flow (CBF) was measured by the non-invasive xenon-133 technique in patients with increased blood viscosity as a result of paraproteinaemia or leukaemia. A highly significant inverse relation was found between CBF and arterial oxygen content in 59 paraproteinaemic patients. There was no significant correlation between CBF and whole blood viscosity, and no significant difference between CBF in paraproteinaemic patients and a matched group of anaemic patients. 7 leukaemic patients with up to threefold increases in whole blood viscosity were also found to have CBF appropriate to their degree of anaemia. The effects of treatment to reduce blood viscosity were studied in 7 paraproteinaemic and 5 leukaemic patients; changes in CBF were significantly related to changes in arterial oxygen content but not to changes in blood viscosity. These studies confirm the importance of arterial oxygen content in the determination of CBF, and demonstrate that regulatory mechanisms can maintain normal cerebral oxygen transport despite increased plasma and whole blood viscosity.

Systemic lupus erythematosus with paraproteinemia

Nine patients (2.2%) in a group of 415 who were followed in a longitudinal prospective study of systemic lupus erythematosus (SLE) were found to have various monoclonal (M) proteins in their blood (IgG [6 patients], IgA [2 patients], IgM [1 patient]). No other findings compatible with plasmacytic dyscrasia were found. Bence Jones proteinuria was absent. Bone marrow aspirates and skeletal radiographs did not reveal any associated features of malignancy. Four of the 9 patients were under the age of 50. From the point of view of the M components, 3 groups emerged: transient (2 patients), persistently stable (6 patients), and increasing serum concentrations (1 patient). Using current measures of disease status, no correlation was apparent between the presence, type, and concentration of the M protein and the clinical and laboratory variables of lupus activity. Thus, M proteins were found in 2% of our SLE patients, but their relationship to the polyclonal B cell activation seen in this disorder, or perhaps to therapeutic modalities used in its treatment, remains to be elucidated.

Multiple myeloma

Multiple myeloma is a malignant neoplasm of plasma cells involving bone and bone marrow, frequently leading to extensive skeletal destruction, bone marrow failure, renal dysfunction, and problems related to the monoclonal myeloma proteins. Vigilant supportive care and effective chemotherapy can prolong survival and improve the quality of life in most patients.

Extramedullary non-gastrointestinal plasmocytoma. An immunohistochemical study of sixteen cases

Sixteen cases of extramedullary non-gastrointestinal plasmocytoma were studied for intracytoplasmic immunoglobulins by means of the immunoperoxidase-complex technique. Of the sixteen cases IgG class were observed in 4, IgM in one and IgA in 9 cases. Kappa light chains were found in 9 cases and lambda light chains in 6 cases. In one case a bitypic pattern of k- and lambda-positivity was encountered. In 2 cases only kappa light and no heavy chains were detected. The predominance of the IgA class in extramedullary, non-gastrointestinal plasmocytomas is in contrast to the prevalence of IgG type in multiple myeloma. The better possible behaviour of IgA-plasmocytomas is discussed further.

B-cell neoplasms with homogeneous cold-reacting antibodies (cold agglutinins)

Among 78 patients with persistent cold agglutinins, 31 had lymphoma, 13 had macroglobulinemia of Waldenstrom, six had chronic lymphocytic leukemia and 28 had chronic cold agglutinin disease. The average age was over 60 years. Patients wit chronic cold agglutinin disease had more hemolytic crises, bleeding and Raynaud's phenomena, and less frequently lymphadenopathy or hepatosplenomegaly. The frequency of anemia, positive Coombs test results, cryoglobulinemia and Bence Jones proteinuria was similar in the various groups. Survival time from diagnosis was on average two years in lymphoma, two and a half years in Waldenstrom's macroglobulinemia, more than six years in chronic lymphocytic leukemia and more than five years in chronic cold agglutinin disease. Anti-I were common in chronic cold agglutinin disease (74 percent) and rare in other groups (32 to 33 percent). Anti-I and other cold agglutinins were rare in chronic cold agglutinin disease and common in lymphoma and Waldenstrom's macroglobulinemia. In chronic cold agglutinin disease, and in Waldenstrom's macroglobulinemia, cold agglutinins usually had K light chains--92 percent and 71 percent, respectively--whereas in lymphoma, 71 percent of cold agglutinins had lambda light chains. The type of light chains related to the specifically of cold agglutinins: 58 percent of IgM/K were anti-I, 75 percent of IgM/lambda had other specificities. Cold agglutinins were cytotoxic to autologous and allogeneic cells were killed implying that the former may be precoated in vivo with the antibodies. In conclusion, conditions with persistent cold agglutinins are a spectrum that varies from "benign" autoimmune-like chronic cold agglutinin disease to malignant lymphoma. Marked differences in the light chain type of cold agglutinins, specificity toward membranous antigens and severity of clinical manifestations were noted in benign and malignant varieties.

Waldenstrom's macroglobulinemia, a hyperviscosity manifestation of venous stasis retinopathy

Waldenstrom's macroglobulinemia is characterized by hyperviscosity. This is usually the result of an increased serum concentration of IgM molecules; this paraprotein has a high molecular weight and unusual shape. The changes in shear rate associated with increased IgM concentrations produces maximal viscosity in the venous circulation. One of the major causes of retinal venous occlusion is venous stasis retinopathy. The typical patient with this disorder is a young individual with a periphlebitis.. However, the hyperviscosity in Waldenstrom's macroglobulinemia is an ideal representative of a venous stasis that is without associated vascular pathology. To illustrate this situation, two cases are described and their etiologic features are discussed.

Paraprotein-induced hyperviscosity. A reversible cause of stroke

Although the occurrence of the hyperviscosity syndrome with IgG plasma cell leukemia is unusual, it should be considered in the evaluation of patients with focal neurologic deficit with or without a known malignant paraproteinemia. If serum viscosity is elevated, then emergent plasmapheresis should be considered, as it may reverse the neurologic deficit.

Multiple myeloma: current concepts in diagnosis and management

The basic pathologic process in multiple myeloma is the neoplastic proliferation of a single clone of plasma cells. Although the events which trigger autonomous cell growth are not well understood, the secretion of an M component, a serum or urinary immunoglobulin molecule or a light chain fragment by the vast majority of myeloma cells has provided a biologic marker which has greatly facilitated the study of this disease Some of the more recent clinical concepts which have evolved from studies on the plasma cell and the immunoglobulin molecule are discussed.

Viscosity, cerebral blood flow and haematocrit in patients with paraproteinaemia

It has been suggested that blood viscosity is involved in the control of cerebral blood flow (CBF) (Thomas et al. 1977a, b, Humphrey et al. 1979). CBF, using the intravenous Xenon133 technique, blood viscosity and haematocrit were measured in 21 patients with elevated viscosity due to paraproteinaemia and found to be the same as in normal subjects. However, the paraproteinaemic patients were anaemic with a mean haematocrit of 0.342. This degree of anaemia would normally be associated with a high CBF. The paraproteinaemic patients were then compared with a group of 10 anaemic patients with matched haematocrits but without paraprotein bands. The whole blood and plasma viscosities were significantly higher in the paraproteinaemic patients and the CBF was significantly lower. The haematocrit, and therefore oxygen carriage, was similar in the two groups. It is likely that in the anaemia of paraproteinaemia the expected increase in CBF did not occur because of the limiting factor of increased viscosity. This suggests that in this instance viscosity rather than oxygen carriage is a major determinant in the control of CBF. This is further emphasized by the better correlation between CBF and blood viscosity than between CBF and haematocrit. It seems likely that viscosity and oxygen carriage are independent variables in the control of CBF.

Priapism and multiple myeloma. Successful treatment with plasmapheresis

Priapism was associated with multiple myeloma and hyperviscosity in a sixty-year-old black male. Plasmapheresis treatment of the hyperviscosity corrected his priapism, and chemotherapy for the underlying multiple myeloma prevented the recurrence of priapism after a chronic intermittent history of seventeen years.

Multiple myeloma (light chain disease) with rheumatoid-like amyloid arthropathy and mu-heavy chain fragment in the serum

A 52 year old man presented with multiple myeloma and widespread amyloidosis involving joints, bursae- carpal tunnels, lymph nodes and subcutaneous tissue. Osteolytic bone lesions and pathologic fracture of the neck of the left femur were found. Bone marrow was infiltrated with both plasmacytes and lymphocytes. The majority of plasma cells contained large cytoplasmic vacuoles. Free kappa II type light chains and mu-heavy chain fragment were detected in the serum, and kappa II type Bence Jones protein was found in the urine. The molecular weight of the mu-heavy chain fragment was found to be approximately 50,000 daltons. An immunofluorescence study, using the double labelling technic, showed that the majority of plasmacytes in bone marrow contained both mu and kappa antigenic determinants in the cytoplasm. A review of the 12 previously described patients with mu-heavy chain fragment in the serum showed a variable clinical picture, thus their natural history and therapeutic response are difficult to evaluate at the present time. It seems that mu-heavy chain fragment can be found in a variety of clinical conditions and that mu-heavy chain disease cannot yet be accepted as a separate clinical entity.

The relationship between serum viscosity, hypervolaemia and clinical manifestations associated with circulating paraprotein

In 44 of 56 patients with malignant paraproteinaemia the relationship of serum viscosity, plasma volume (PV), estimated blood volume (BV) and clinical findings was investigated and in the remaining 12 patients one or more of these parameters was studied. There was a correlation between increased PV and serum viscosity (r = 0.66, P less than 0.001). The retinopathy characteristic of the hyperviscosity syndrome (HVS) was always associated with serum viscosity greater than or equal to 3.8 and with hypervolaemia. The evidence that the retinal changes were related more closely to serum hyperviscosity than to hypervolaemia is twofold. First, there was a considerable overlap in the degree of BV expansion, but not serum hyperviscosity, in patients with and without retinopathy. Second, the retinopathy in a patient with Waldenström's macroglobulinaemia (WM) improved after plasma exchange with little change in BV. While bleeding was often associated with retinopathy seven patients with multiple myeloma (MM) had no retinopathy, viscosities greater than or equal to 4.3 and BV in the same range as patients with no clinical signs. Haemorrhage in such patients may thus be unrelated to the property of the paraprotein responsible for hyperviscosity. Measurements of PV in a patient with WM having repeated plasma exchanges for bleeding suggested that hypervolaemia may contribute to haemorrhage in some patients. It is suggested that the term 'HVS' should be restricted to patients with retinopathy and that hypervolaemia should be considered a characteristic feature of this syndrome.

Myelomatosis and the hyperviscosity syndrome

Eleven patients are described in whom myelomatosis was complicated by the laboratory and clinical features of the hyperviscosity syndrome (HVS). The myeloma type was IgA in nine and IgG3 in two. In those patients with IgA myeloma the HVS was related to the presence of high molecular weight complexes in the serum. Remission of clinical features was obtained in all patients by plasma exchange. Clinical improvement coincided with reduction of whole blood viscosity and in those patients with IgA myeloma, with a parallel reduction of the high molecular weight complexes. The relationship between the IgA complexes and blood viscosity has been examined by physicochemical analysis of purified IgA monomer and polymers and evidence is presented to show that the IgA polymer has a higher intrinsic viscosity and axial ratio than the larger IgM molecule. The significance of these observations is discussed.

Polyclonal hyperviscosity syndrome

The clinical course of two patients who presented with polyclonal hyperviscosity syndrome is described. Polymerizing IgG rheumatoid factors were isolated from the serum of both patients. The presence of these polymers with their extraordinary rheologic properties was the principal determinant of the abnormal rheological properties of the plasma. Neither patient had a discrete rheumatic disease. In both, a lymphoproliferative syndrome was present with features suggestive of the "pseudolymphoma" of Sjögren's syndrome.

Unusual presentations of multiple myeloma

Multiple myeloma has many unusual manifestations, which may obscure the true cause and delay proper treatment. Physicians in all specialties should be alert to this possibility, since myeloma may be at the root of such diverse disorders as carpal tunnel syndrome, peripheral neuropathy, solitary lytic bone lesions, hypercalcemia, and hyperviscosity syndrome.

Paraproteinemia: blood hyperviscosity and clinical manifestations

Many of the clinical features of paraproteinemia result from impairment of blood flow through the vascular tree because of blood hyperviscosity. Studies were carried out in 65 patients with serum paraproteins (31 with IgG, 25 with IgM, and 9 with IgA) to examine the relationship between the blood viscosity and the frequency of selected clinical features. The blood and plasma viscosities were measured at low rates of shear. Blood hyperviscosity was present in 91% of the patients and plasma hyperviscosity in 75% of the patients. In each of the three immunoglobulin classes both the blood and plasma viscosities increased logarithmically with the paraprotein concentration being greatest in the case of IgM. In addition, the relationship between the hematocrit and the logarithm of blood viscosity tended to be linear at any given protein concentration. In patients with very high levels of paraprotein the blood viscosity was modified by low hematocrits; the latter was below 30 in 70% of patients in whom the concentration of paraprotein was above 4 g/100 ml. The prevalence of clinical complications involving the retinal circulation, the peripheral vascular system, and the central nervous system increased markedly with increasing blood viscosity, measured at 0.18 S-1. One or more of these regions was affected in greater than 80% of patients with blood viscosity above 60 centipoise and in less than 23% of patients with blood viscosity below 40 centipoise. These observations illustrate the complex relationship between blood viscosity, concentration of paraprotein, immunoglobulin class and hematocrit, and emphasize the importance of measuring the whole blood viscosity at low rates of shear in determining the risk of vascular complications.

Relationship between paraprotein polymerization and clinical features in IgA myeloma

The clinical manifestation fo IgA multiple myeloma are usually not considered distinguishable from those of IgG myeloma despite the fact that IgA differs from IgG in several characteristics, particularly molecular size heterogeneity. The clinical and laboratory features of 25 patients with IgA myeloma seen during a 5 year period are presented. The degree of paraprotein polymerization was observed to vary greatly in these patients but remained chronologically constant in six individuals studied on several occasions over this period. The patients were divided into two groups on the basis of the degree of paraprotein polymerization. The first group comprised those patients in whom the IgA paraprotein was greater than 50% polymerized, whilst in the second group the paraprotein was predominantly monomeric. No clinical or pathological differences were seen between the 'polymeric' and 'monomeric' groups of myeloma apart from that directly attributable to the physicochemical effect of the paraprotein polymerization. Thus, five patients out of 11 of the 'polymeric' group had developed the hyperviscosity syndrome, whilst no patients in the 'monomeric' group had developed this complication. The concentration of the paraprotein during the course of the disease was comparable in both groups. This syndrome is considered to be relatively common in IgA myeloma and adds to the morbidity and mortality of the disease. Its anticipation and treatment may improve the quality and survival of patients likely to develop this complication.