Cryoglobulinemia

Etiology

Cryoglobulin is normally present in healthy individuals at low levels. Experts theorize that these levels indicate the existence of immune complexes actively working to clear this protein by immunoglobulins with RF activity.[2][6]

The prime risk factor for cryoglobulinemia is drug use, as 90% of cases of cryoglobulinemic vasculitis are associated with HCV infections. The formation of hepatitis C IgG and IgM RF causes the immune complex formation and complement activation, leading to blood vessel inflammation. In addition, cryoglobulinemia is also associated with monoclonal gammopathies (such as multiple myeloma, Waldenström macroglobulinemia, or MGUS), monoclonal gammopathies of renal significance, and connective tissue diseases (such as SLE and Sjögren syndrome).

Epidemiology

Cryoglobulinemia is a rare condition and is clinically significant in about 1 in 100,000 individuals, with a higher prevalence observed in southern Europe. Cryoglobulins have been identified in several patient populations, specifically 15% to 20% of HIV-infected individuals, 40% to 65% of HCV-infected patients, and over 90% of HIV/HCV-coinfected individuals.[7][8][9][10][11] In addition, the condition is also linked to autoimmune diseases, such as SLE and Sjögren syndrome, as well as hematologic malignancies, such as multiple myeloma and lymphoma.

Cryoglobulinemia predominantly affects adults, with a higher incidence observed in females than males. Based on the currently available case series, patients with type 1 cryoglobulin account for 5% to 25% of the cases. Geographic variations in prevalence are noted, correlating with the distribution of HCV infection and other associated diseases. Due to its association with various underlying conditions, the epidemiology of cryoglobulinemia reflects a complex interplay between genetic, environmental, and infectious factors.

Pathophysiology

Chronic immune stimulation and lymphoproliferation lead to increased production of higher levels of mono-, oligo-, or polyclonal immunoglobulins, which subsequently form cryoglobulins. These cryoglobulins circulate in the blood and can precipitate, forming immune complexes that deposit in small- to medium-sized blood vessels, leading to vascular occlusion and inflammation. The deposition triggers an inflammatory response, causing endothelial cell injury and attracting immune cells such as lymphocytes and macrophages to the site. In addition, the immune complexes activate the complement system, further contributing to inflammation and tissue damage. Organs commonly affected include the skin, kidneys, and peripheral nerves, with clinical manifestations such as purpura, glomerulonephritis, and neuropathy.

Histopathology

Tissue biopsy reveals small-vessel leukocytoclastic vasculitis, indicating inflammation of the blood vessels. Histological findings typically include endothelial cell swelling, fibrinoid necrosis of the vessel walls, and perivascular infiltrates of lymphocytes, macrophages, and neutrophils.

Hypersensitivity vasculitis or angiitis is evident in 50% of cases, while inflammatory or noninflammatory purpura is present in 15%. Noninflammatory hyaline thrombosis, more common in type I cryoglobulinemia, is observed in 10% of cases.[12] In cryoglobulinemia, vasculitis is the most common finding, whereas hyperviscosity syndrome is the least common.[13]

Renal complications of cryoglobulinemia occur in up to half of patients with HCV positivity. The most common pattern, seen in up to 90% of cases, is membranoproliferative glomerulonephritis, often referred to as "cryoglobulinemic glomerulonephritis."[14][15] Common manifestations include endocapillary hypercellularity, mainly composed of monocytes, duplication of the peripheral basement membrane, and the presence of intercapillary pseudothrombi.[16][17][18] These pseudothrombi, or hyaline thrombi, represent immune complex deposits in the mesangial, subendothelial, and capillary walls or lumens.[15] Characteristic features include glomerular monocytes or macrophages (CD68+) and low C4 levels. Glomerular necrosis and crescent formation are evident in less than 5% of cases, while mesangial proliferation varies.

History and Physical

A documented history of various conditions can help identify cryoglobulinemia. Some conditions commonly associated with this disease include clonal hematologic disease (myeloma and MGUS), autoimmune diseases, infections with HBV, HCV, or HIV, skin purpura on lower limbs, skin ulcers under cold conditions, and acute foot or wrist drop suggestive of neuropathy from ischemia. 

Notable clinical features include arthralgias (44%), purpura (75%), skin ulcers (16%), glomerulonephritis (35%), and peripheral neuropathy (57%). Careful attention is required if these symptoms occur alongside a clonal hematologic disorder.

Clinical Classification of Cryoglobulinemia

The presentation of cryoglobulinemia can vary significantly, with a majority of cases being asymptomatic. Cryoglobulinemia can clinically be classified as mentioned below.

Type I cryoglobulinemia: Type I presents with vascular symptoms, including ischemia, livedo reticularis (an erythematous, reticulated pattern that appears lace-like and blanches with pressure), and skin necrosis.[19][20][21][22] This type most commonly exhibits skin manifestations with a frequency of approximately 70% to 85%. While exercising caution regarding the diagnosis, prompt treatment of the skin abnormalities is essential to prevent the development of digital gangrene.

During initial studies of this specific type of cryoglobulinemia, French researchers initiated a nationwide study involving 64 patients with expressed symptoms over 15 years.[19] All patients exhibited cutaneous associations, often resulting in ulcers and necrosis. Typical findings also included peripheral neuropathy, arthralgia, and arthritis. None of the participants in this study showed any central nervous system (CNS), pulmonary, cardiac, or gastrointestinal symptoms.

Type II/III (mixed) cryoglobulinemia: The presentation of mixed cryoglobulinemia is commonly associated with underlying symptoms such as arthralgia, fatigue, and myalgia. Also, palpable purpura related to vasculitis or sensory changes due to peripheral neuropathy are common with type II/III.[23] 

The symptoms usually seen are referred to as "Meltzer triad," consisting of purpura, arthralgias, and weakness. Meltzer triad is detected early in the clinical presentation in approximately 80% of patients.[24] The most prevailing symptom of mixed cryoglobulinemia is purpura, typically observed on the legs, extending up to the torso and/or upper extremities.[21] Usual symptoms persist for approximately 1 to 2 weeks, with intermittent episodes occurring 1 to 2 times per month.

Evaluation

The most predictive measure for cryoglobulinemia is the measurement of cryoglobulin coupled with a low C4 complement level. This combination is typical of cryoglobulinemia syndromes.[25] 

In the lab detection of cryoglobulins, approximately 10 to 20 mL of blood is collected and prepared at 37 °C without the addition of anticoagulants. The serum is centrifuged and then refrigerated to allow the precipitation of cryoglobulin. Type I cryoglobulinemia presents as a precipitate within 24 hours, with a 3- to 5-day window. Type II/III presents with precipitation approximately 5 to 7 days after initial refrigeration.

A cryocrit is defined as the percentage of cryoglobulin compared to the total serum volume read from a calibrated sedimentation tube. Although this method is convenient, rapid, and inexpensive, it is also found to be dubious in terms of reproducibility. Generally, the cryocrit in individuals without cryoglobulinemia is close to zero, and a cryocrit greater than 0.5% to 1% or a concentration greater than 50 mcg/mL is significant.[25][26][27] 

In type II cryoglobinemia, the cryocrit is between 2% and 7%, while type III demonstrates results around 1% to 3%. Type I cryoglobulinemia, associated with IgM monoclonal gammopathies, tends to have a higher cryocrit than type II; the latter virtually never manifests hyperviscosity.[28] The strengths of a cryocrit test are few, and its weaknesses tend to overshadow its clinical utility. Notably, a decrease in the cryocrit over the treatment time may indicate success.[29] Although symptoms do not correlate with the cryocrit.[28] The cryocrit (and complement levels) do not reflect disease activity.[30] Only the presence of symptoms should determine the initiation of therapy. Asymptomatic patients, even those with a high cryocrit, are said to require no treatment at all. 

Another common method of evaluating cryoglobulinemia is immunochemical analysis. Immunofixation is performed on dissolved cryoglobulin by antibodies with specified heavy/light chains. This test allows for the specific categorization of the type after the initial diagnosis. Other lab testing includes urinalysis, complement serum analysis, RF levels, viral serologies, and analysis of acute-phase reactants. In particular cases, specific testing is performed for further evaluation. One such test is the biopsy of organs impacted by the disease, which is used to acquire additional information. Type I cryoglobulinemia is generally seen in the skin, kidney, and bone marrow and is associated with thromboses. Type II/III presents within the skin, kidney, and peripheral nervous system.

Electromyography (EMG) is another test used in situations where neuromuscular disease is evident. Lastly, imaging studies can be utilized to confirm the presence of cryoglobulinemia. However, it is important not to rely solely on imaging for evaluation; the specified clinical presentation should guide these tests.

Renal complications of cryoglobulinemia occur in upwards of half of patients with HCV positivity. They typically occur 3 to 5 years after the purpura appears and most commonly take the form of membranoproliferative glomerulonephritis.[15][4] A renal biopsy can provide data on the extent of the disease.

Treatment / Management

The treatment of cryoglobulinemia depends on the underlying primary disorder, severity, and nature of organ involvement. In presentations of mixed cryoglobulinemia with symptoms, the treatment is directed at the underlying autoimmune or infectious disorders. In the case of essential mixed cryoglobulinemia, the clinical course is more severe, and the recommended treatment is steroids combined with rituximab, with the steroids to be tapered. In addition, the treatment for cryoglobulinemia focuses on each individual case and includes plasmapheresis and immunosuppression (such as glucocorticoids and rituximab) for patients with rapidly progressing or life-threatening outcomes. The treatment is directed toward the underlying infection or autoimmune disorder. Generally, the treatment is tailored to address the underlying (causal) disease, the presence of hyperviscosity, and any co-occurring organ involvement or damage.

HCV infections most commonly cause mixed cryoglobulinemia. The connection between infection and autoimmune or lymphoproliferative disorders is common. The general onset of this disease is slow-paced, but in some situations, rapid progression can occur. In recent years, with the advent of direct antiviral therapy, there has been a change in the treatment approach.[4] HCV-positive patients with cryoglobulinemia are now recommended to receive initial therapy with pan-genotypic antiviral regimens (such as sofosbuvir or velpatasvir and glecaprevir or pibrentasvir). HCV genotyping and subtyping should continue, but initial treatment is still important.(B3)

Studies have demonstrated a response rate with minimal viral counts in almost 100% of patients, although about 13% experience a relapse.[21] The administration of antivirals in HCV-B-cell clonalities is necessary to eliminate the viral threat, especially considering the immunosuppressives used to obliterate the clone. Direct antiviral agents have a better tolerability and safety profile than interferon (IFN), with the latter exhibiting a superior anti-lymphoma effect.[4][31] There were no significant differences in overall survival or progression-free survival between the 2 treatments.(B3)

Cyclophosphamide has been utilized alongside apheresis to address high cryocrit levels and prevent a post-apheresis rebound in cryoglobulin synthesis. However, its usage has diminished due to the rise of B-cell–depleting monoclonal antibodies such as rituximab. When using rituximab, close monitoring of patients with latent HBV infection is essential, and appropriate prophylaxis should be provided. Monitoring HBV DNA or hepatitis B surface antigen (HBsAg) is also recommended. Low-dose monoclonal antibodies or concurrent administration of an antiviral regimen may offer additional benefits. 

Classification Based on Disease Severity

The apparent severity of the disease guides healthcare professionals on how best to treat the patient. Although there is no established outline for severity designations, the descriptions below are used for guidance.

Mild disease: Healthcare professionals typically do not prescribe immunosuppressive treatment in cases classified as mild. Instead, the focus lies on treating the underlying disease.

Manifestations of mild disease often include a petechial rash without lesions, arthralgia without apparent organ damage, and mild sensory neuropathy.

Moderate-to-severe disease: In this clinical scenario, immunosuppressive treatment may not be necessary, as the primary focus remains on treating the underlying (causative) disease.

In this classification, the presentation includes:

• Progressive neuropathy
• Pulmonary vasculitis
• CNS vasculitis presenting as a stroke or cognitive impairment
• Gastrointestinal vasculitis associated with bleeding and abdominal pain
• Digital ischemia

The aforementioned clinical indicators do not comprise a complete list of manifestations.

A comprehensive treatment plan for managing mixed cryoglobulinemia typically involves pain management, wound care, and preventive measures against infections. Appropriate prophylaxis is crucial, particularly for patients undergoing steroid or immunosuppressive therapy. The treatment strategy should be tailored to address the disease's existing etiology.

In moderate-to-severe cases, the specialized focus is to address the primary symptoms with immunosuppressive therapy. Typically, immunosuppressive therapy is initiated until a steady state is achieved, followed by the devised regimen. For patients with HIV or HBV, antiviral therapy should be initiated before or alongside immunosuppressive treatment. A combination of high-dose glucocorticoids and rituximab is recommended as an initial treatment approach for moderate to severe cryoglobulinemia.

Rituximab has demonstrated effectiveness in treating cryoglobulinemia by improving vasculitis, reducing RF levels, normalizing C4 complement levels, and depleting B-cell clones in both bone marrow and peripheral blood.[4][32] However, its use comes with potential toxicities, such as life-threatening vasculitis flares, serum sickness syndrome, and exacerbation of HCV viremia. Maintenance therapy with rituximab is recommended for cases of severe, life-threatening vasculitis.[33](B3)

Cyclophosphamide, combined with apheresis, has effectively addressed high cryocrit levels, which contribute to hyperviscosity syndrome in cryoglobulinemia, and has prevented post-apheresis rebound in cryoglobulin synthesis.[4] Cyclophosphamide can also be administered concurrently with steroids. However, the role of steroids appears to be limited, as they are not typically used in maintenance therapy. Cyclophosphamide and rituximab are known to have steroid-sparing effects.(B3)

Presently, apheresis is considered a second-line treatment option for cryoglobulinemic vasculitis.[4] However, as outlined below, apheresis is crucial in severe conditions, which include the following:(B3)

• Hyperviscosity syndrome (especially with a cryocrit exceeds 10%) 
• Skin ulcers caused by cutaneous vasculitis
• Life-threatening, multiorgan cryoglobulinemic vasculitis
• Rapidly progressing renal failure
• Refractory neuropathy

For apheresis, the recommended course typically involves daily exchanges approximately 3 times per week over a couple of weeks. Double-filtration plasmapheresis has also successfully treated cryoglobulinemic vasculitis, leading to a faster and more sustained response.[34] Despite its effectiveness, therapeutic apheresis now assumes a more subordinate role, albeit with a favorable safety profile.[4] This rapidly reduces cryoglobulins and viral particles, primarily addressing hyperviscosity concerns. Cyclophosphamide or steroids are often administered to counteract any post-apheresis rebound in cryoglobulins. Notably, apheresis usage in cryoglobulinemic patients with renal involvement has shown a high response rate of 78%, with most patients experiencing long-term recovery.[35](A1)

Steroids and cyclophosphamide are frequently administered alongside apheresis to mitigate the risk of a post-apheresis rebound in cryoglobulin production. Cyclophosphamide, along with rituximab, can also serve as steroid-sparing agents. However, their use is approached cautiously due to the associated risk of infection. Steroids, on the other hand, are believed to have no maintenance role in the treatment of cryoglobulinemic vasculitis. 

Patients undergoing immunosuppressive treatments for cryoglobulinemia necessitate close monitoring, the extent of which hinges on the severity of the condition. During physical examinations, particular attention should be paid to skin involvement and the presence of digital ischemia.

In cases involving kidney treatment, close monitoring of blood pressure, creatinine levels, complement levels, RF levels, and urinalysis is necessary. Patients with progressive glomerulonephritis should undergo weekly observation, while those with conditions exhibiting slower disease progression can be evaluated monthly. The extent of organ involvement significantly influences the prescribed regimen and overall prognosis. Individuals with intestinal vasculitis or acute gastrointestinal or pulmonary hemorrhage typically face poor outcomes.

Patients with cryoglobulinemic vasculitis are considered "immunologically frail."[18][4] Therefore, it is strongly recommended that those patients receive vaccinations against influenza, pneumococci, varicella zoster, and COVID-19. Vaccination should ideally occur before administering steroids or immunosuppressive drugs. If patients are already undergoing treatment with rituximab or other immunosuppressives, vaccination should be delayed for at least 6 months after the last infusion or 4 weeks before the next infusion to optimize response. Notably, COVID-19 vaccinations have been associated with relapses of cryoglobulinemic vasculitis, sometimes leading to renal damage.[16][17][18] The risk of a vasculitis flare triggered by the vaccine is notable, yet the benefits of vaccination are deemed to outweigh these risks.(B3)

Differential Diagnosis

Cryoglobulinemia must be diagnosed carefully, as its clinical presentation is similar to other vasculitides affecting small- or medium-sized vessels. The differential diagnoses of cryoglobulinemia include:

• Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (such as granulomatosis with polyangiitis [Wegener], eosinophilic granulomatosis with polyangiitis [Churg-Strauss], and microscopic polyangiitis).
• IgA vasculitis (Henoch-Schönlein purpura).
• Cutaneous small-vessel vasculitis.
• Hypersensitivity vasculitis.
• Vasculitis associated with a connective tissue disorder (such as SLE, rheumatoid arthritis, and Sjögren syndrome).

Other thrombotic and embolic disorders, such as thrombotic thrombocytopenic purpura and hemolytic uremic syndrome, should also be considered in the differential diagnosis. Additionally, patients affected by chronic HCV infection may develop arthralgias and membranoproliferative nephritis even without cryoglobulinemia. Therefore, further testing is necessary to reach a definitive diagnosis.

Prognosis

When assessing the prognosis of cryoglobulinemia, the patient's underlying condition must be considered to determine the disease's extent accurately. Specifically, when considering type 1 cryoglobulinemia, hematologic diseases are often a preexisting condition.[22] Studies have shown that the presence of cryoglobulins in the blood does not indicate a higher mortality rate.

Survival rates with cryoglobulinemia are 70% after 10 years of evident symptoms and approximately 50% 10 years after diagnosis. The prognosis largely depends on comorbidities and their severity, as well as the effectiveness of treatment.[36] Recent trials with the CD-20 antibody rituximab have shown some beneficial results, and its use is being favored.[37]

HCV-related cryoglobulinemia vasculitis is a significant disease with an approximate 5-year mortality rate of 25%.[1][38] Prognosis, aside from liver fibrosis, usually depends on the status of the kidneys, CNS, heart, and gastrointestinal tract. The vascularity associated with these organs is affected and contributes heavily to the prognosis. Renal failure is shown to be higher in those with HCV compared to mixed cryoglobulinemia.

Complications

Complications associated with cryoglobulinemia typically affect the outcomes of prognoses. Studies have indicated that complications usually result in lower chances of survival for a patient. Common complications include renal failure and the underlying development of a lymphoproliferative disorder.

HCV-related indolent non-Hodgkin lymphoma has been successfully treated with direct antiviral therapy alone.[4] However, for higher-grade lymphomas, the use of antivirals during the peri-chemotherapy period remains an open decision.

Renal complications of cryoglobulinemia occur in upward of half of the patients with HCV positivity, typically 3 to 5 years after the onset of purpura, and most commonly manifest as membranoproliferative glomerulonephritis.[4] A renal biopsy can provide data on the extent of the disease, and the overall prognosis is poor. Indolent renal effects can be addressed with antivirals, while severe effects warrant immunosuppressives supplemented by steroids and apheresis. Even if a sustained virologic response is achieved, organ recovery often lags.