Cryoglobulinemic vasculitis: pathophysiological mechanisms and diagnosis

PURPOSE OF REVIEW

Cryoglobulins (CG) are immunoglobulins that precipitate in the cold, and dissolve at 37°C. In vivo, in cold exposed tissues and organs, they can induce vasculitis and occlusive vasculopathy after deposition on vascular endothelium under low temperature and high concentration conditions. Clinical manifestations are cutaneous (purpura, ulcers, vasomotor symptoms, and livedo reticularis), rheumatological (arthralgia and arthritis), and peripheral neuropathy (paresthesia and pain in the lower limbs). In profound organs such as the kidneys, CG deposition is less temperature-dependent, favored by local protein and anion concentrations, and can lead to glomerulonephritis. This review will focus on cryoglobulinemic vasculitis and vascular lesion, and their diagnosis.

RECENT FINDINGS

The mechanisms of vascular lesions of pathogenic CG in function of CG type and their characteristics are better defined. Optimal conditions for CG detection are critical. The importance of looking for underlying diseases, especially hepatitis C virus status in mixed CG, is reminded.

SUMMARY

A decision diagram for CG vasculitis diagnosis based on clinical and biological parameters is proposed.

Renal-limited Cryoglobulinemic Vasculitis: Two Case Reports

Cryoglobulinemic vasculitis (CV) presents with systemic manifestations, including renal disease, arthritis, peripheral neuropathy, and muscle weakness. We encountered two patients who developed severe nephrotic range proteinuria; however, extrarenal manifestations were not noted during the clinical course. A renal biopsy revealed typical membranoproliferative glomerulonephritis (MPGN) with huge thrombus-like endothelial deposits and predominant IgM positivity, but electron microscopy did not reveal any definite microtubules. Immunosuppressive therapy and plasmapheresis were only partially effective, and the improvement was not durable. Biological therapy with rituximab (RTX) had no effect. Renal-limited CV should be recognized as a subset of essential CV.

[Renal damage caused by Rhupus syndrome associated with anti-neutrophil cytoplasmic antibodies vasculitis and cryoglobulinemia]

We analyzed the clinicopathological characteristics of one patient with Rhupus syndrome associated nephropathy in Peking University People's Hospital, and reviewed the related literature. The patient was a middle aged female. She developed rheumatoid arthritis first, and then manifested mild systemic lupus erythematosus together with positive anti-neutrophil cytoplasmic antibodies (ANCA) and cryoglobulinemia several years later. The renal biopsy was performed and manifested as lupus nephritis. The transmission electron microscopy revealed cryoglobulinemia associated renal damage. This report shows that the clinicopathological characteristics in patients with Rhupus syndrome associated nephropathy are complicated. The renal pathology can be used as a diagnostic tool.

Thyroid involvement in hepatitis C - associated mixed cryoglobulinemia

OBJECTIVE

The prevalence and clinical features of thyroid involvement in patients with hepatitis C virus-associated mixed cryoglobulinemia (MC+HCV) have been reviewed.

DESIGN

A PubMed Medline search was conducted through December 2011 to identify all studies that reported thyroid involvement in MC+HCV patients. Reference lists of the papers initially detected were manually searched to identify additional relevant reports. Studies had to contain sufficient and clear information to be included.

RESULTS

In MC+HCV patients, the following thyroid autoimmune abnormalities were significantly more frequent than in controls: high levels of serum anti-thyroperoxidase autoantibody (AbTPO); high levels of serum AbTPO and/or anti-thyroglobulin autoantibody; humoral and ultrasonographical signs of thyroid autoimmunity (35% vs 16%); prevalence of subclinical hypothyroidism (11% vs 2%). Also, the prevalence of papillary thyroid cancer has been found higher in MC+HCV patients than in controls, in particular in patients with autoimmune thyroiditis. The involvement of T helper 1 immunity and chemokine (C-X-C motif) ligand 10 (CXCL10) may be the pathogenetic basis of the association between MC+HCV and thyroid autoimmunity.

CONCLUSION

These results show a high prevalence of thyroid disorders in patients with MC+HCV and point to the need for careful monitoring of thyroid function in these patients.

[The role of endothelial dysfunction in progression of liver fibrosis and manifestation of сryoglobulinemia syndrome in patients with chronic hepatitis C]

The study of 78 patients with chronic hepatitis C is presented. It was found that emergence and progression of endothelium-dependent dysfunction of endothelium is combined with progression of liver fibrosis. The manifestation of clinical signs of the HCV-associated crioglobulinemia syndrome is registered in patients with stage F 3-4 liver fibrosis against the background of high concentration of the mixed cryoglobulins, rheumatoid factor of Ig M and the expressed endothelium-dependent dysfunction of endothelium.

Health-related quality of life in severe cryoglobulinaemic vasculitis and improvement after B-cell depleting therapy

OBJECTIVES

To study the health-related quality of life (HRQOL) in severe cryoglobulinaemic vasculitis (CV) associated with hepatitis C virus infection (HCV) and to describe the effect of rituximab on HRQOL.

METHODS

HRQOL was evaluated with the Medical Outcomes Study Short Form 36 (SF-36). Health Survey questionnaire was submitted to 15 patients with severe CV. SF-36 questionnaire was evaluated at baseline and after rituximab. Physical Health Composite Summary (PCS) and Mental Health Composite Summary (MCS) scores were calculated according to standard protocols, and normalised to healthy controls. SF-36 summary scores were compared with those of HCV positive patients without CV, and other vasculitis published in the literature. European Quality of Life-5 dimensions (EQ5D) scores were also derived.

RESULTS

Physical and mental domain scores were all reduced if compared with those of the healthy population, with physical domains being greatly affected. HRQOL of CV was comparable with HRQOL reported for the other small vessel vasculitis. The development of CV in HCV positive patients worsened PCS rather than MCS score. Birmingham Vasculitis Activity Score (BVAS) did not correlate with HRQOL, while the presence of peripheral neuropathy was associated with a worse HRQOL. Early rituximab treatment improved both PCS and MCS scores, with long-term effects.

CONCLUSIONS

PCS rather than MCS was affected in HCV positive patients when CV is present. Rituximab improved both physical and mental domains, thus supporting its use before antiviral therapy in severe HCV-related CV. The cost/benefits ratio of a sequential therapy may be supported.

The cryoglobulinaemias

Cryoglobulins are immunoglobulins that precipitate in vitro at temperatures less than 37°C and produce organ damage through two main pathways: vascular sludging (hyperviscosity syndrome, mainly in type I cryoglobulinaemia) and immune-mediated mechanisms (principally vasculitis, in mixed cryoglobulinaemia). Cryoglobulinaemia is associated with many illnesses, which can be broadly grouped into infections, autoimmune disorders, and malignancies; the most common cause is infection with hepatitis C virus. Mixed cryoglobulinaemic syndrome is diagnosed when a patient has typical organ involvement (mainly skin, kidney, or peripheral nerve) and circulating cryoglobulins. Cutaneous purpura is the most common manifestation of cryoglobulinaemic vasculitis. The most frequently affected internal organs are the peripheral nerves, kidneys, and joints. The course varies widely and prognosis is influenced by both cryoglobulinaemic damage to vital organs and by comorbidities associated with underlying diseases. More than 90% of cases of cryoglobulinaemia have a known underlying cause; therefore treatment is focused on the cause of the disorder rather than merely symptomatic relief. Studies suggest that both combined or sequential antiviral therapies and targeted biological treatments might be more effective than monotherapy.

Hepatitis C virus-mixed cryoglobulinemia-lymphoma relationship

HCV (hepatitis C virus) chronic hepatitis has become one the most expensive diseases for public health systems all over the world in the past 10-20 years, a real epidemic, the second most frequent, after hepatitis B virus infection. Due to the complex manifestations, one may consider HCV infection as a "systemic" disease. Mixed cryoglobulinemia (MC) is the most common extrahepatic manifestation of HCV infection, but cryoglobulinemic vasculitis (CV) is considered to be relatively sparse although prevalence studies are needed. Presence of serum cryoglobulins is essential for MC diagnosis, but serum levels do not correlate with the disease activity or prognosis. MC can be defined as a B lymphocyte proliferation disease being characterized by polyclonal activation and antibody synthesis. Evolution to lymphoma should be considered continuous but also other infectious, environmental or genetic factors could be involved. The t (14.18) translocation and Bcl-2 activation in B lymphocytes, B cell-activating factor (BAFF), E2-CD81 interaction, immunoregulatory T CD4+CD25(high) + lymphocytes and type III IFNs might play an important role in MC and lymphoma evolution in HCV patients.

Mixed cryoglobulinemia

Mixed cryoglobulinemia (MC), type II and type III, refers to the presence of circulating cryoprecipitable immune complexes in the serum and manifests clinically by a classical triad of purpura, weakness and arthralgias. It is considered to be a rare disorder, but its true prevalence remains unknown. The disease is more common in Southern Europe than in Northern Europe or Northern America. The prevalence of 'essential' MC is reported as approximately 1:100,000 (with a female-to-male ratio 3:1), but this term is now used to refer to a minority of MC patients only. MC is characterized by variable organ involvement including skin lesions (orthostatic purpura, ulcers), chronic hepatitis, membranoproliferative glomerulonephritis, peripheral neuropathy, diffuse vasculitis, and, less frequently, interstitial lung involvement and endocrine disorders. Some patients may develop lymphatic and hepatic malignancies, usually as a late complication. MC may be associated with numerous infectious or immunological diseases. When isolated, MC may represent a distinct disease, the so-called 'essential' MC. The etiopathogenesis of MC is not completely understood. Hepatitis C virus (HCV) infection is suggested to play a causative role, with the contribution of genetic and/or environmental factors. Moreover, MC may be associated with other infectious agents or immunological disorders, such as human immunodeficiency virus (HIV) infection or primary Sjögren's syndrome. Diagnosis is based on clinical and laboratory findings. Circulating mixed cryoglobulins, low C4 levels and orthostatic skin purpura are the hallmarks of the disease. Leukocytoclastic vasculitis involving medium- and, more often, small-sized blood vessels is the typical pathological finding, easily detectable by means of skin biopsy of recent vasculitic lesions. Differential diagnoses include a wide range of systemic, infectious and neoplastic disorders, mainly autoimmune hepatitis, Sjögren's syndrome, polyarthritis, and B-cell lymphomas. The first-line treatment of MC should focus on eradication of HCV by combined interferon-ribavirin treatment. Pathogenetic treatments (immunosuppressors, corticosteroids, and/or plasmapheresis) should be tailored to each patient according to the progression and severity of the clinical manifestations. Long-term monitoring is recommended in all MC patients to assure timely diagnosis and treatment of the life-threatening complications. The overall prognosis is poorer in patients with renal disease, liver failure, lymphoproliferative disease and malignancies.

Rituximab for the treatment of glomerulonephritis in hepatitis C associated cryoglobulinaemia

Mixed-type cryoglobulins are strongly associated with hepatitis C virus (HCV) infection and may lead to vasculitis with renal involvement. The treatment of this condition is antiviral therapy for HCV, but this may be ineffective or not tolerated because of side effects. Alternative strategies such as immunosuppressive drugs and plasmapheresis are of limited use, especially in patients after liver transplantation (LTx). We describe an LTx patient with cryoglobulinaemia-associated glomerulonephritis, who was treated successfully with the B cell depleting monoclonal antibody rituximab.

[Possible causes of temperature-dependent disorders of regional circulation in cryoglobulinemia]

We studied effects of changed blood theology in cryoglobulinemia on temperature-dependent disorders of peripheral circulation. The rheological status was assessed by aggregation characteristics of blood at temperature 37 degrees C and 4 degrees C at nephelometry of reverse light diffusion. Blood cryoglobulins concentration was determined spectrophotometrically. Turbidimetry estimated the size of cryocomplexes at different temperatures and energetic characteristics of their formation. It was found that blood of healthy donors in cooling does not change its rheological properties significantly. Blood of patients with cryoglobulinemia cooled to 4 degrees accelerated formation of linear erythrocyte aggregates and increased their strength. The results agreed with estimated values of molecular connection energy in cryocomplexes. The greatest difference between the patients' and donors' blood was in strength of the largest aggregates. Sharp strengthening of both large and small aggregates in blood cooling makes vascular red cell desaggregation impossible. This may entail microcirculatory arrest.

Case of mononeuritis multiplex onset with rituximab therapy for Waldenström's macroglobulinemia

Waldenström's macroglobulinemia (WM) is a lymphoplasmacytic disorder with associated monoclonal gammopathy. A wide variety of neuropathies can be associated with WM, but most commonly it is a mild length-dependent sensory neuropathy of unclear etiology. Rituximab is a monoclonal antibody which suppresses mature B-cell populations. It has increasingly been used in wide applications including WM, especially in those cases with severe neuropathy. The highlighted case provides an example of rituximab treatment complication in a WM patient with mild sensory neuropathy that evolved to multiple mononeuropathies with features of systemic vasculitis and unusual conversion of type I to type II cryoglobulinemia.

Treatment of hepatitis C-virus-related glomerulonephritis

Membranoproliferative glomerulonephritis (MPGN) associated with type II cryoglobulinemia is the predominant type of hepatitis C virus (HCV)-related glomerulonephritis. The blockade of the renin-angiotensin system, as well as a combined anti-HCV therapy that associates standard or pegylated alpha-interferon with ribavirin, are mandatory in all patients experiencing an HCV-related glomerulonephritis. In patients with nephrotic-range proteinuria and/or progressive renal failure, immunosuppressive therapy is necessary. Rituximab, the monoclonal anti-CD20 antibody that selectively targets the B cells, seems to be as least as efficient as cyclophosphamide. Because it is also better tolerated, it should be preferred to cyclophosphamide. During the acute phase, plasmapheresis and steroid pulses can be used. However, future prospective, controlled, and randomized studies are still required to establish evidence-based guidelines to treat HCV-related glomerulopathies.

Natural history and therapy of 66 patients with mixed cryoglobulinemia

Cryoglobulinemia, a relatively uncommon disorder, is classified into types I, II, and III, with type II consisting of a monoclonal immunoglobulin possessing activity toward a polyclonal component. Many disease associations and therapies have been described but clinical trials are few, and the natural history, causes, therapy, and pathways of cryoglobulinemia require further investigation. Here, we describe the symptoms, comorbidities, treatments, and response of 66 patients with type II cryoglobulinemia by examining the records of all patients evaluated at Mayo Clinic, Rochester, Minnesota, between 3/2/1994 and 11/27/2000, using our prospective dysproteinemia database. Symptoms varied greatly among patients and during the disease course. Most common were purpura (55% of patients), renal disease (26%), edema (24%), neuropathy (18%), and arthralgia (21%). Renal disease required the most aggressive intervention. Laboratory findings did not correlate with disease manifestations or severity. Only age was a significant predictor of mortality. Ten patients had cryoglobulinemia without an identified comorbidity. Thirty-three patients had viral hepatitis alone, 6 had a lymphoproliferative disorder alone, and 5 had a rheumatologic disease alone. Ten patients had a combination of disorders, such that hepatitis C was identified in a total of 40 patients, lymphoproliferative disorders in 16, and rheumatologic disease in 8. Twenty-two different treatments were administered. Corticosteroids were the most common treatment, followed by interferon with or without ribavirin. Type II cryoglobulinemia is a nonfatal disease most frequently associated with hepatitis C. Treatment is generally directed at the underlying condition. Not all patients require treatment, and many can be followed and treated symptomatically.

Prevalence and characteristics of peripheral neuropathy in hepatitis C virus population

OBJECTIVE

To assess the prevalence of peripheral neuropathy (PN) and its correlation with cryoglobulinemia (CG) in an unselected, untreated referral hepatitis C virus (HCV) population.

PATIENTS AND METHODS

Two hundred and thirty four patients (120 women and 114 men) with untreated HCV infection were consecutively enrolled by seven Italian centres. Clinical neuropathy was diagnosed when symptoms and signs of peripheral sensory or motor involvement were present. Median, ulnar, peroneal, and sural nerves were explored in all patients and distal symmetric polyneuropathy was diagnosed when all explored nerves or both lower limb nerves were affected. Mononeuropathy and mononeuropathy multiplex were diagnosed when one nerve or two non-contiguous nerves with asymmetrical distribution were affected. Screening for CG was done in 191 unselected patients.

RESULTS

Clinical signs of PN were observed in 25 of the 234 patients (10.6%). Electrophysiological PN was found in 36 (15.3%). CG was present in 56/191 patients (29.3%). The prevalence of CG increased significantly with age (p<0.001) and disease duration (p<0.05). PN was present in 12/56 (21%) patients with CG and 18/135 (13%) without CG (p=NS). PN increased significantly with age (p<0.001) and logistic regression analysis confirmed age as the only independent predictor of PN (OR 1.10 for each year; 95% CI 1.04 to 1.15; p<0.001).

CONCLUSIONS

Electrophysiological examination detected subclinical neuropathy in 11 patients (4.7%). Statistical analysis showed that CG was not a risk factor for PN whereas PN prevalence increased significantly with age.

Paraproteinemic neuropathies

The occurrence of a peripheral neuropathy (PN) in association with a monoclonal gammopathy is quite common and suggests that monoclonal proteins may play a pathogenetic role in peripheral nervous system damage. In fact, paraproteinemic PN constitute an heterogeneous group of disorders related to various pathogenetic factors, and the histopathologic features in peripheral nerve biopsies differ from one condition to another. In several well defined disorders, the responsibility of the monoclonal component in the development of the PN has been evidenced. This is the case for most of the PN associated with an IgM monoclonal gammopathy, either a monoclonal gammopathy of undetermined significance (MGUS) or Waldenstrom's macroglobulinemia. The responsibility of the monoclonal protein in the occurrence of amyloid neuropathy related to multiple myeloma is also recognized. However, most IgG or IgA MGUS, as well as the monoclonal component in POEMS syndrome, have an uncertain causal relationship with the neuropathy. PN associated with monoclonal cryoglobulin (type 1) are occasional and differ from those associated with mixed cryoglobulins (types 2 or 3).

Q fever endocarditis masquerading as Mixed cryoglobulinemia type II. A case report and review of the literature

Background

The clinical manifestations of Q fever endocarditis are protean in nature. Mixed cryoglobulinemia type II is rarely a facet of the presenting clinical manifestations of Q fever endocarditis.

Case presentation

We report a case of a 65-year-old pensioner with such an association and review the literature. As transesophageal echocardiograms are usually normal and blood cultures are usually negative in Q fever endocarditis, many of the manifestations (fever, rash, glomerulonephritis/evidence of renal disease, low serum C4 complement component, presence of mixed type II cryoglobulin, constitutional symptoms as arthralgias and fatigue) can be attributed to Mixed cryoglobulinemia type II per se. The use of Classic Duke Endocarditis Service criteria does not always suffice for the diagnosis of Q fever.

Conclusion

The application of the modified criteria proposed by Fournier et al for the improvement of the diagnosis of Q fever endocarditis will help to reach the diagnosis earlier and thus reduce the high mortality of the disease. We would like to stress the importance of ruling out the diagnosis of Q fever endocarditis in cases of mixed type II cryoglobulinemia.

[Systemic vasculitis due to hepatitis C virus]

Hepatitis C virus (HCV) is the leading cause of chronic liver disease in industrialized countries. HCV also causes a variety of extrahepatic disorders, of which systemic vasculitis, of the cryoglobulin or polyarteritis nodosa type, is the most severe. This article reviews the main diagnostic, pathophysiologic and therapeutic aspects of HCV-induced systemic vasculitis.

Cryofibrinogenemia associated with polyarteritis nodosa

We report the case of a 77-year-old woman with biopsy-confirmed polyarteritis nodosa (PAN) associated with cryofibrinogenemia presenting with polyarthralgia and digital gangrene induced by cold exposure. The clinical manifestations and parameters measured by laboratory markers including cryofibrinogen responded well to corticosteroid therapy. To our knowledge, the case of the combination of PAN and cryofibrinogenemia has not been reported. Our case indicates that cryofibrinogenemia might be associated with PAN. The PAN patients with cold-induced symptoms should be screened for cryofibrinogen.

A case of progression from type II cryoglobulinaemia to Waldenstrom's macroglobulinaemia in a patient with chronic hepatitis C

Hepatitis C infection is associated with B-cell lymphoproliferative disorders, including mixed cryoglobulinaemia and B-cell lymphoma. A direct pathogenetic role of this infection in lymphomagenesis has been suggested but the molecular basis for viral induced B-cell proliferation is still unknown. We report an unusual case of a patient affected by chronic hepatitis C who presented severe type II cryoglobulinaemia and subsequently lymphoplasmacytoid lymphoma consistent with Waldenstrom's macroglobulinaemia and type I cryoglobulinaemia. In this patient antiviral treatment induced beneficial effects.

Clinical spectrum of cryoglobulinaemic neuropathy

BACKGROUND AND OBJECTIVE

Cryoglobulinaemic neuropathy (CN) is probably common, as it is usually related to HCV infection. The aim of this study was to delineate the clinical spectrum of CN in a large series and to investigate the factors influencing its expression.

METHODS

Seventy one consecutive patients (12 men, 59 women), diagnosed as having CN on the basis of clinical features of neuropathy, clinical and serological findings of mixed cryoglobulinaemia, and exclusion criteria, were identified during a six year period. All patients underwent clinical examination, and electrophysiological and laboratory investigations.

RESULTS

Results of the patients with "pure" CN (n = 54) and those with comorbidities (n = 17) were evaluated separately. Of the former 76% had sensory neuropathy (including selective small fibre sensory neuropathy (SFSN) in 14 patients), 15% had sensorimotor polyneuropathy, and 9% had mononeuritis multiplex. The pattern of distribution was similar in the patients with comorbidities. In 30/54 patients, CN was the first manifestation of cryoglobulinaemia. Patients with mild cryoglobulinaemic syndrome had sensory neuropathy more frequently than patients with active syndrome (p < 0.001), in particular SFSN (p < 0.001). The latter group had more severe features, with significantly more cases of reduced or absent motor (p = 0.028) and sensory action potentials (p < 0.001), and a tendency towards higher Rankin scores (p = 0.06).

CONCLUSIONS

Sensory neuropathy, often in the form of SFSN, is by far the commonest form of CN. Cryoglobulinaemia should be vigorously investigated in the diagnosis of sensory neuropathy, especially in older women. Activity of the cryoglobulinaemic syndrome is a major factor influencing the clinical expression and severity of CN.

Cold Agglutinin Disease and Cryoglobulinemia

Cold agglutinin disease is a form of direct, extravascular, antiglobulin-positive hemolysis. In vivo, immunoglobulin (Ig) M fixes complement molecules to the red cell membrane. Successive passages through the mononuclear phagocyte system result in loss of red cell membrane. The resultant spherocytes lose resiliency and are ultimately lost from the circulation extravascularly. The high concentration of complement molecules on the red cell surfaces makes this syndrome resistant to the standard therapies for immune-mediated hemolysis. Rituximab has been reported to reduce the severity of hemolysis. Type II cryoglobulins are composed of a monoclonal IgM and a polyclonal IgG. These complexes have rheumatoid factor activity and can produce immune-complex vasculitis. The target organs are the skin, nerves, kidney, liver, and joints. More than 80% of patients have evidence of hepatitis C infection. Interferon and interferon plus ribavirin have been shown to produce serologic responses. When vasculitis is active, corticosteroids are often required to permit healing of ulcers in the skin or to treat the membranoproliferative glomerulonephritis that is seen, thereby preventing loss of renal function. Rituximab therapy has been found to be effective in mixed cryoglobulinemia, with decreases in cryoglobulin values and improvement in complement values.

Cl- regulates cryoglobulin structure: a new hypothesis for the physiopathological mechanism of temperature non-dependent cryoprecipitation

Cryoglobulins are pathological cold-precipitable immunoglobulins associated with a number of infectious, autoimmune and neoplastic disorders. Patients, when exposed to low temperatures, show symptoms related to intravascular precipitation of such immunoglobulins. The formation of cryoaggregates induced by exposure to cold temperature is the key pathogenetic mechanism. The subsequent intravascular precipitation can account for some clinical signs of peripheral vasculitis, but fails to explain the precipitation of cryoglobulins in regions where no significant temperature changes take place. We studied, in vitro, the activity of different ions on temperature-dependent aggregation of cryoglobulins and found that the concentration of Cl- present in solution is the most important variable that controls the size and the rate of formation of aggregates, both at low temperature and at 37 degrees C. We suggest that chloride anion could be the most important factor involved in the pathogenesis of events in visceral regions, such as in the kidneys, where no temperature changes occur but where the local Cl- concentration changes to maintain blood electrolytic homeostasis and acid-basic equilibrium. Moreover, identification of a specific structural domain responsible for Cl- binding may provide new targets for drugs selectively designed to interfere with cryoglobulin aggregation.

Hepatitis C virus-associated extrahepatic manifestations: a review

The hepatitis C virus (HCV) infection is a worldwide disease that is characterized by a preferential chronic evolution with mild to severe liver disease, including cirrhosis and, in lesser proportion, hepatocarcinoma. Out of these complications, HCV is frequently reported to complicate extrahepatic manifestations. Among those associated to HCV infection with a high degree of certainty, mixed cryoglobulinemia and its complications (skin, neurological, renal, rheumatological involvement) are the most prevalent (50%) in HCV-infected patients. The other diseases include noncryoglobulinemic systemic vasculitis, splenic lymphoma with villous lymphocytes, fatigue, porphyria cutanea tarda, sicca syndrome, and autoantibodies production. The extrahepatic manifestations that share mild-degree certainty of association with HCV infection include B-cell non-Hodgkin lymphoma, autoimmune thrombocytopenia, pruritus, and type II diabetes mellitus. The other diseases such as autoimmune thyroiditis, lichen planus are more questionable for their eventual association with HCV and others (pulmonary fibrosis with or without polymyositis, progressive encephalomyelitis, Mooren's corneal ulcers, erythema nodosum, chronic polyradiculonevritis) are mostly case reports. Howerver, even in cases of tight association, the mechanisms through which HCV may promote or induce extrahepatic manifestations remain unclear and merit further investigations.

Neurologic manifestations in primary Sjögren syndrome: a study of 82 patients

Neurologic involvement occurs in approximately 20% of patients with primary Sjögren syndrome (SS). However, the diagnosis of SS with neurologic involvement is sometimes difficult, and central nervous system (CNS) manifestations have been described rarely. We conducted the current study to describe the clinical and laboratory features of SS patients with neurologic manifestations and to report their clinical outcome. We retrospectively studied 82 patients (65 women and 17 men) with neurologic manifestations associated with primary SS, as defined by the 2002 American-European criteria. The mean age at neurologic onset was 53 years. Neurologic involvement frequently preceded the diagnosis of SS (81% of patients). Fifty-six patients had CNS disorders, which were mostly focal or multifocal. Twenty-nine patients had spinal cord involvement (acute myelopathy [n = 12], chronic myelopathy [n = 16], or motor neuron disease [n = 1]). Thirty-three patients had brain involvement and 13 patients had optic neuropathy. The disease mimicked relapsing-remitting multiple sclerosis (MS) in 10 patients and primary progressive MS in 13 patients. We also recorded diffuse CNS symptoms: some of the patients presented seizures (n = 7), cognitive dysfunction (n = 9), and encephalopathy (n = 2). Fifty-one patients had peripheral nervous system involvement (PNS). Symmetric axonal sensorimotor polyneuropathy with a predominance of sensory symptoms or pure sensory neuropathy occurred most frequently (n = 28), followed by cranial nerve involvement affecting trigeminal, facial, or cochlear nerves (n = 16). Multiple mononeuropathy (n = 7), myositis (n = 2), and polyradiculoneuropathy (n = 1) were also observed. Thirty percent of patients (all with CNS involvement) had oligoclonal bands. Visual evoked potentials were abnormal in 61% of the patients tested. Fifty-eight patients had magnetic resonance imaging (MRI) of the brain. Of these, 70% presented white matter lesions and 40% met the radiologic criteria for MS. Thirty-nine patients had a spinal cord MRI. Abnormalities were observed only in patients with spinal cord involvement. Among the 29 patients with myelopathy, 75% had T2-weighted hyperintensities. Patients with PNS manifestations had frequent extraglandular complications of SS. Anti-Ro/SSA or anti-La/SSB antibodies were detected in 21% of patients at the diagnosis of SS and in 43% of patients during the follow-up (mean follow-up, 10 yr). Biologic abnormalities were more frequently observed in patients with PNS involvement than in those with CNS involvement (p < 0.01). Fifty-two percent of patients had severe disability, and were more likely to have CNS involvement than PNS involvement (p < 0.001). Treatment by cyclophosphamide allowed a partial recovery or stabilization in patients with myelopathy (92%) or multiple mononeuropathy (100%). The current study underlines the diversity of neurologic complications of SS. The frequency of neurologic manifestations revealing SS and of negative biologic features, especially in the event of CNS involvement, could explain why SS is frequently misdiagnosed. Screening for SS should be systematically performed in cases of acute or chronic myelopathy, axonal sensorimotor neuropathy, or cranial nerve involvement. The outcome is frequently severe, especially in patients with CNS involvement. Our study also underlines the efficacy of cyclophosphamide in myelopathy and multiple neuropathy occurring during SS.

An approach to the diagnosis and treatment of cryofibrinogenemia

Cryofibrinogenemia is a rarely symptomatic disorder that is underrecognized due to the infrequency with which it causes symptoms. Although completely reversible, this disorder can be life threatening when untreated. In this review, the classification, pathophysiology, and clinical presentation of cryofibrinogenemia are described, based on case reports and prospective observational data. Diagnostic criteria are outlined, and therapies are assessed critically. This information should help clinicians in establishing a diagnosis of cryofibrinogenemia and initiating treatment.

Extrahepatic manifestations of hepatitis C infection

Hepatitis C virus (HCV) affects 1.8% of the American population, and approximately 38% of patients with HCV will manifest symptoms of at least 1 extrahepatic manifestation during the illness. Renal disease, neuropathy, lymphoma, and Sjögren syndrome with or without mixed cryoglobulinemia are all strongly associated with HCV infection. Porphyria cutanea tarda and diabetes have also been linked to HCV. Most extrahepatic manifestations of chronic HCV infection are immunological, and the chronic infection seems to be necessary for their development. The molecular study of the unique way in which the HCV virus interacts with the human immune system is beginning to provide plausible explanations of the pathogenic role of HCV in some of these syndromes, but many pathogenetic links remain completely obscure.

[Anti-GM1 and anti-sulphatide antibodies in systemic idiopathic vasculitis, systemic lupus erythematosus and mixed cryoglobulinaemia: Serum detection and clinical and electrophysiologic correlations]

BACKGROUND

In the last two decades increasing interest has been focused on the association between autoimmune polyneuropathies and high titers of anti-nervous serum autoantibodies. High titer of IgG anti-GM1 antibody could be detected in Guillain Barre' syndrome and in chronic painful axonal sensory immune-mediated polyneuropathy. The possible occurrence of anti-nervous autoantibodies in autoimmune diseases not limited to the nervous system is still under study.

METHODS

We evaluated 29 patients with systemic lupus erythematosus (SLE), 19 with biopsy-proven renal involvement, 28 patients with mixed IgM-K/IgG polyclonal cryoglobulinaemia (18 with glomerulonephritis) and 19 with small-sized vessel ANCA-associated vasculitis (12 with renal involvement) by using a sensitive immunoenzyme method of autoantibody detection.

RESULTS

Compared to controls (1/176+/-1/205; 1:204+/-1:103), we found a significant increase in plasma IgM and IgG anti-GM1 titers (1:643+/-1:531; 1:444+/-1:309) in SLE patients (p<0.0001). We also found IgM (1:3032+/-1:2844) and IgG (1:1560) anti-sulphatide titers to be higher than the control group (p<0.0001). Mean plasma IgM and IgG anti-GM1 titers of the cryoglobulinaemic patients were 1:524+/-1:403 and 1:501+/-1:415, respectively, once again higher than the controls (p<0.0001). Mean plasma IgM and IgG anti-sulphatide titers in this group were 1:1864+/-1:1189 and 1:1350 (p<0.0001). We found idiopathic systemic vasculitis patients to have significantly increased levels of anti-sulphatides IgG class autoantibodies (1:1400; p<0.0001). We found no correlation with the serologic markers for vasculitis or the clinical or histologic extent of renal involvement. Electrophysiologic studies revealed that in 38% of SLE patients (p<0.005), 61% of cryoglobulinaemic patients (p<0.01) and 42% of ANCA-related vasculitic patients (p<0.01) the abnormal titers of antineuronal antibodies were associated with clinical or subclinical evidence of neuropathy.

CONCLUSIONS

In patients with systemic idiopathic or secondary vasculitis anti-GM1 and anti-sulphatide antibodies can frequently be found. Their presence should prompt an accurate neurological examination because these serologic abnormalities are significantly associated with neurologic, often subclinical, involvement. Antineuronal reactivity might be the epiphenomenon of primary phylogistic damage, which exposes normally segregated neuronal epitopes or be directly involved in triggering neurological injury.

Kidney and liver involvement in cryoglobulinemia

Cryoglobulinemia is a pathological condition characterized by the presence in the blood of a group of proteins (cryoglobulins) showing the common property of precipitating from cooled serum. Mixed cryoglobulins (MCs) are composed of a polyclonal immunoglobulin G (IgG) bound to another immunoglobulin that acts as an anti-IgG rheumatoid factor; 2 types of MCs can be identified. The origin is not clear in 30% of all MCs, and this subset of cryoglobulinemias is called "essential." The great majority (up to 90%) of patients with essential MC (EMC) of both types has been related to HCV infection. The renal involvement in essential MC has been observed in 2% to 50% of patients in reported series. A well-characterized pattern of glomerular disease termed "cryoglobulinemic glomerulonephritis" is present in individuals with type-II EMCs in serum and IgMk RF being the most frequent monoclonal component. Aspecific and infrequent glomerular lesions occur in EMC patients with type III cryoglobulins. The most frequent histologic picture of cryoglobulinemic GN is that of membranoproliferative GN (MPGN) with subendothelial deposits. However, cryoglobulinemic GN may have some distinctive features that differentiate it from idiopathic type-I MPGN. Evidence of liver involvement has been found in 60% to 80% of EMC patients. Recent data support the notion that the stage of liver disease in patients with type II or III MC has association with the prevalence of cryoglobulinemia. Few controlled trials have been published on the treatment of HCV-related MC; in addition, the majority of the patients enrolled in these trials had an unclear renal involvement. Interferon (IFN) is an effective drug for the treatment of patients with HCV-associated MC and cryoglobulinemic GN. In the presence of acute cryoglobulinemic GN, IFN does not prevent progression of renal damage; combination therapy with cytotoxic ad anti-inflammatory drugs, and sometimes plasma exchange, is recommended. Prospective controlled trials are underway on this purpose.

Mixed cryoglobulinemia secondary to interferon therapy for hepatitis C: case report & review of the literature

Mixed cryoglobulinemia is a systemic vasculitis associated with hepatitis C infection. We present a case of mixed cryoglobulinemia induced by interferon-alpha therapy for hepatitis C infection and review previous cases in which cryoglobulinemic symptom exacerbations were caused by interferon-alpha.

Glomerulonephritis with microtubular deposits associated with cryoglobulinemia and chronic active hepatitis

A 65-year-old-woman presented with edema, ascites, proteinuria and abnormal liver function tests. A small amount of mixed cryoglobulin was detected in her serum. Liver biopsy revealed mild chronic active hepatitis, but tests for hepatotropic viral infection were negative. Electron microscopy of the renal biopsy revealed glomerular electron-dense deposits that contained numerous tubular structures. Renal amyloidosis and light chain deposition disease were ruled out by appropriate histological techniques. The ultrastructural findings of renal biopsy suggested either cryoglobulinemic glomerulonephritis or immunotactoid glomerulopathy. Although the exact interrelationship among the peculiar glomerulopathy, cryoglobulinemia and chronic active hepatitis in the present case remains undetermined, this report enlarges the spectrum of glomerulopathy characterized by extracellular deposition of microtubules.

Hepatitis C virus-associated mixed cryoglobulinemia. Clinical manifestations, histopathological changes, mechanisms of cryoprecipitation and options of treatment

Chronic hepatitis C virus (HCV) infection is frequently associated with a variety of autoimmune phenomenons. Mixed cryoglobulinemia (MC) appears in up to 50% of chronic HCV-infected patients. Cryoglobulins consist of immunoglobulin complexes precipitating in vitro when cooled below body temperature. In most cases IgM with rheumatoid factor activity is found in cryoprecipitates which could lead to vasculitis induced by the deposition of immnuocomplexes in small vessels. This vasculitis is thought to cause clinical symptoms called Meltzer's triad. This triad is represented by purpura, arthralgia and weakness. One third of patients suffering from HCV-associated mixed cryoglobulinemia are developing typical symptoms during their course of disease. The striking association between HCV infection and MC has conduced to the hypothesis that HCV is of major importance in the production of MC with followed vasculitis. Both hepatrophism and lymphotrophism have been reported for the hepatitis C virus. Infection of B-cells by HCV could probably lead to a bcl-2 translocation and immunoglobulin gene rearrangement which results in clonal lymphoproliferation and in synthesis of monoclonal IgM with rheumatoid factor activity. These IgM form immunocomplexes with IgG in the cold, which are finally responsible for the described vasculitis. Histopathological changes of the liver are dominated by chronic HCV infection. The majority of times mild activity of hepatitis or mild fibrosis could be found. Nevertheless, cirrhosis is more often found in HCV-infected patients suffering from MC compared to patients without MC. Conventional treatment of MC is aimed to reduce circulating immune complexes by immunosupression and plasmapheresis. With the emerging concept of a viral pathogenesis the therapeutic approach has changed during the last decade. Interferon treatment of MC, particularly of HCV-associated MC is well established nowadays.

[Laser Doppler imaging and cryoglobulinemia]

Continuous microcirculation monitoring of the right foot was carried out for the first time in a 62-year-old patient with cryoglobulinaemia prior to, during and after manual needle insertion at Jie Xi(St.41) acupuncture point using a new method of laser Doppler perfusion imaging (PIMII, Lisca AB, Linköping, Sweden). In addition to visual inspection, changes in mean perfusion were also used as evaluation parameters. Our results suggest that the new biomedical technique of laser Doppler imaging is a useful method for monitoring the effects of acupuncture on the peripheral microcirculation.

Therapeutic apheresis for the renal complications of multiple myeloma and the dysglobulinemias

Disordered immunoglobulin synthesis can result in a variety of different types of renal pathology. Multiple myeloma is often associated with the overproduction of light chains which may result in toxicity to the renal tubules and acute renal failure. Patients with mixed cryoglobulinemia will have renal involvement which is most often in the form of a membranoproliferative glomerulonephritis. Renal involvement in macroglobulinemia is relatively uncommon, but IgM thrombi can be so voluminous as to occlude the glomerular capillary lumen. In each of these examples, therapeutic plasma exchange has been found to be a useful adjunct to the eventual chemotherapy required for the definitive treatment of these disorders.

The lymphoid system in hepatitis C virus infection: autoimmunity, mixed cryoglobulinemia, and Overt B-cell malignancy

Like other hepatotropic viruses, hepatitis C virus (HCV) shares the property of inducing hepatocellular damage, possibly through induction of immune mechanisms that lead to hepatocellular necrosis. After infection of hepatocytes, and possibly other cells, humoral and cellular responses occur aimed at prevention of virus dissemination and elimination of infected cells. The early activated mechanisms include production of nonspecific and specific antibodies that represent the first-line of defense against invading foreign pathogens. As a consequence, circulating immune complexes are promptly formed, and antigen uptake and processing by specialized cells are enhanced. A major fraction of circulating immunoglobulins (Igs) are part of the spectrum of the so-called natural antibodies, which include anti-idiotypic antibodies and molecules with rheumatoid factor (RF) activity. They mainly belong to the IgM class, are polyclonal, and have no intrinsic pathogenetic potential. In 20-30% of HCV-infected patients, RFs share characteristics of high affinity molecules, are monoclonal in nature, and result in the production of cold-precipitating immune complexes and mixed cryoglobulinemia. It has been shown that anti-idiotypic antibodies and polyclonal and monoclonal RF molecules have the same cross-reactive idiotype, called WA, suggesting that their production is highly restricted. This strongly indicates that they arise from stimulation with the same antigen, likely HCV. It has also been speculated that B-1 (CD5+) and B-2 (CD5-) B-cell subsets, which use a limited number of VH germline genes, underlie the production of low-affinity polyclonal and high-affinity monoclonal antibodies, respectively. The persistent production of monoclonal RF molecules implies the existence of a further mechanism capable of restricting the reactivity and reflects a distinct selection of a cell population that can be maintained throughout life because they are continuously exposed to antigen pressure. Either polyclonal or monoclonal profiles of B-cell expansion are demonstrable in the liver of most HCV-infected patients. The occurrence of B-cell clonal expansion is strictly related to intrahepatic production of RF molecules, and this suggests that liver is a microenvironment, other than lymphoid tissue, in which a germinal centerlike reaction is induced. The frequent detection of oligoclonal B-cell expansion may, indeed, represent a key pathobiologic feature that sustains nonmalignant B-cell lymphoproliferation. The preferential expansion of one clone would in turn lead to a monoclonal pattern that could favor stochastic oncogenic events. It can be postulated that HCV is the stimulus not only for the apparent benign lymphoproliferative process underlying a wide spectrum of clinical features, but also for the progression to frank lymphoid malignancy in a subgroup of patients. Current data indicate a higher prevalence of overt B-cell non-Hodgkin's lymphoma in HCV-infected patients, especially in some geographic areas.

Systemic vasculitis in patients with hepatitis C

OBJECTIVE

To analyze the main characteristics of patients infected with hepatitis C virus (HCV) presenting with different types of vasculitis syndrome.

METHODS

We retrospectively compared 2 groups of patients with HCV presenting with systemic vasculitis: 10 with biopsy proven polyarteritis nodosa-type systemic vasculitis (PAN, Group 1) and 7 with mixed cryoglobulinemia syndrome (MC, Group 2).

RESULTS

Patients of Group 1 presented with different features than Group 2: life threatening systemic vasculitis (10 vs 0; p < 0.01), severe multifocal sensorimotor mononeuropathies versus distal moderate sensory polyneuropathies, malignant hypertension (5 vs 0; p = 0.04), cerebral angiitis (2 vs 0), ischemic abdominal pain (2 vs 0), kidney and liver microaneurisms (2 vs 0), increased erythrocyte sedimentation rate and C-reactive protein (7 vs 0; p < 0.01), renal insufficiency (5 vs 0; p = 0.04), HCV genotype 1b (3 vs 6; p = 0.06), and lower activity of chronic hepatitis (p = 0.02). Neuromuscular biopsies showed lesions of vasculitis in all patients, but the type of vasculitis was different in Group 1 compared to Group 2: medium size artery involvement (7 vs 0; p < 0.01), necrotizing vasculitis (10 vs 0; p < 0.01), and mononuclear cell infiltrate in perivascular areas (0 vs 7; p < 0.01). Using prednisone, plasma exchanges, and interferon-alpha, complete recovery was obtained in all PAN-type patients except one. In Group 2 patients, interferon-alpha did not have any effect on the peripheral neuropathy.

CONCLUSION

HCV infection may be associated with different types of systemic vasculitis, i.e., polyarteritis nodosa or mixed cryoglobulinemia. Because of differences in clinical and pathological features and therapeutic strategy, PAN-type vasculitis should be distinguished from MC-type vasculitis in HCV patients.

Relapsing ischemic encephaloenteropathy and cryoglobulinemia

Cryoglobulinemia is a rare cause of encephalopathy. The authors report three patients with strikingly similar clinical features of recurrent encephalopathy accompanied by symptoms of gastrointestinal ischemia. In only one patient was cryoglobulinemia ascertained in life during the final illness. The autopsy examinations all showed diffuse cerebral, enteral, and systemic small vessel lesions immunoreactive for immunoglobulins and typical of mixed essential cryoglobulinemia. This unusual relapsing clinical syndrome is readily misinterpreted as of nonorganic origin despite its potentially fatal prognosis.

Cryofibrinogenaemia: a study of 49 patients

The purpose of this study was to characterize the clinical features and components of 30 patients with isolated cryofibrinogen (CF) versus those of 19 patients with combined CF and cryoglobulins (CG). Secondary forms of cryofibrinogenaemia associated with collagen disorders, infectious or malignant diseases, were significantly more frequent in patients with combined CF and CG than those with isolated CF (79 versus 47%, P = 0.02). Both groups of CF patients presented predominantly cutaneous symptoms (77% in isolated CF; 58% in combined CF + CG), and less frequently venous and/or arterial thrombosis (13% in isolated CF; 3% in combined CF + CG). Patients with idiopathic forms of CF, and particularly those without CG, suffered essentially from recurrent painful skin ulcers, mainly triggered by cold exposure. Patients with isolated CF had higher mean plasma concentrations of CF than those with combined CF + CG (1. 61 +/- 1.26 versus 0.82 +/- 1.18 g/l, respectively; P = 0.004), but there was no correlation between the CF plasma level and either the severity of symptoms or the sensitivity to cold. In patients with isolated CF, fibronectin was suggested (by precipitation analysis) to be a major component of the cryoprecipitate, whereas immunoglobulins were rarely present (in only three out of 30 patients). By contrast, in the majority of patients (78%) with combined CF and CG, the CF consisted mainly of immunoglobulins of the same class as those characterizing the associated CG. Analysis of the CG precipitate revealed the presence of fibronectin but not fibrinogen, alpha1-antitrypsin and alpha2-macroglobulin. In conclusion, isolated and combined cryofibrinogenaemia are associated with different clinical signs requiring different clinical management, but there is no evidence as yet for a causal role of the cryoprecipitates in the differences observed.

[Mixed cryoglobulinemia]

Cryoglobulins are immunoglobulins that persist in serum, precipitate with cold temperature, and resolve when rewarmed. Cryoglobulinemia are part of systemic vasculitis, and they are in the subgroup of immune complex type vasculitis. Mixed cryoglobulinemia are associated with malignant B lymphoproliferative disorders, auto-immune and chronic infectious diseases, particularly hepatitis C virus infection. Mixed cryoglobulinaemia has a variable prognosis, depending mainly on renal involvement, systemic extension, and severity of hypertension. In pilot studies, alpha interferon seemed promising to treat symptomatic mixed cryoglobulinemia, because of its immunomodulating and antiviral properties. In severe or resistant forms of mixed cryoglobulinemia, plasmapheresis or immunosuppressive agents may be useful.

Mixed cryoglobulinemia in hepatitis C patients. GERMIVIC

Cryoglobulins are immunoglobulins that persist in the serum, precipitate with cold temperature and resolubilize when rewarmed. Types II and III are mixed cryoglobulins (MC), composed of different immunoglobulins, with a monoclonal component in type II and only polyclonal immunoglobulins in type III. Mixed cryoglobulins are associated with connective-tissue disease, malignant hematological disorder (type B lymphoproliferation) or obvious infectious process. Mixed cryoglobulinemia syndrome is characterized by the clinical triad of purpura, arthralgia and asthenia associated with type II or type III MC. The disorder is the consequence of an immune-complex-type vasculitis as supported by clinical features, analysis of the cryoglobulins, the usually depressed level of complement during the active phase of the disease, and the deposition of immunoglobulins and complement in the lesions. Such cryoglobulinemia vasculitis may involve numerous organs, particularly the peripheral nervous system and the kidneys. MC is frequently associated with clinical and biological evidence of liver disease. There has been some controversy about which comes first, MC or chronic liver disease, but it seems fairly clear that MC is often a manifestation of underlying chronic active or persistent hepatitis. In MC patients, the hepatotropic antigen(s) capable of triggering production of antibodies which can later form immune complexes has been sought for many years. In the last ten years, numerous studies have demonstrated that infection with hepatitis C virus is involved in the pathogenesis of most mixed cryoglobulinemia. This review analyzes the main published data on hepatitis C virus-mixed cryoglobulinemia, the role of liver alterations, the predictive factors associated with MC production in HCV patients and its symptomatic nature or not, and the different types of vasculitis associated with HCV chronic infection.

Clonality and specificity of cryoglobulins associated with HCV: pathophysiological implications

BACKGROUND/AIMS

Hepatitis C virus (HCV) infection plays a central role in the pathogenesis of mixed cryoglobulinemia through molecular mechanisms which remain to be elucidated. The aim of this study was to investigate the role of antibody responses to HCV in the pathogenesis of cryoglobulinemia through characterization of the anti-HCV specificity and immunochemical characteristics of the immunoglobulins involved in cryoprecipitation.

METHODS

Sera from 50 consecutive patients with chronic HCV infection (RNA positive) were screened for the presence of cryoglobulins. The two major components of cryoprecipitates, IgM rheumatoid factors and IgG, were separated by high performance liquid chromatography and analyzed for immunochemical composition by immunoblotting and antibody specificity by ELISA and immunoblotting using recombinant HCV proteins and synthetic peptides as antigens.

RESULTS

Cryoprecipitates were observed in 27 patients and characterized by immunofixation: 13 (48%) were classified as type II and 14 (52%) as type III. Monoclonal immunoglobulins were detected by immunoblotting in 20 cryoprecipitates: IgM in 14 samples and IgG in 14, with a clear preponderance of IgG3 (12/14). Specificity studies on sera and purified IgM and IgG fractions from cryoprecipitates revealed enrichment in cryoglobulins, predominantly polyclonal IgG1, reactive with the HCV structural proteins, whereas specificities for nonstructural viral proteins were relatively less represented compared to whole serum. No restricted pattern of fine specificity was observed. IgG3 subclass was apparently not involved in HCV nucleoprotein binding.

CONCLUSIONS

Our findings do not support a direct link between monoclonal cryoglobulins and immune response to HCV According to the proposed pathogenetic model, HCV infection can induce the formation of cryoprecipitable rheumatoid factors, sustain their production, and eventually lead to monoclonal B-cell expansion through several cooperative mechanisms.