Long term outcome of patients with low level of cryoglobulin (<0.05g/L)

Cryoglobulinemia

Cryoglobulins are immunoglobulins that precipitate in vitro at temperatures below 37 ̊C. Cryoglobulin-associated disease is heterogeneous, as not all patients present with it, includes various syndromic presentations (vasculitis is the most common, hyperviscosity syndrome is more exceptional), and can be associated with acute clinical pictures with high mortality. Until the appearance of specific antiviral treatments, the main aetiology has been chronic HCV infection, and currently it is mainly associated with systemic autoimmune diseases, malignant neoplasms and cases with no identified aetiology (essential cryoglobulinemia). Treatment should be modulated according to the predominant etiopathogenesis (vasculitis or hyperviscosity), the severity of internal organ involvement and, especially, the associated underlying disease. Due to the complex aetiological, clinical and pathological scenario of cryoglobulinaemia, early recognition of the most common clinical presentations, a comprehensive clinical assessment of the different organs that may be affected, and multidisciplinary work led by a unit specialised in systemic autoimmune diseases is essential.

Cryoglobulins: Identification, classification, and novel biomarkers of mysterious proteins

Cryoglobulins consist of serum immunoglobulins that precipitate below 37°C and resolubilize upon warming. The clinical triad of cryoglobulinemia usually includes purpura, weakness, and arthralgia. Cryoglobulinemic syndrome, clinically defined as a systemic vasculitis, is associated with chronic infection with hepatitis C virus (HCV) and autoimmune disorders and can evolve into B-cell malignancies. While the current literature about HCV-associated cryoglobulinemia is not very limited, little is known about the immunologic and serologic profiles of affected patients. Therefore, comprehension of the pathogenetic mechanisms underlying cryoprecipitation could be very helpful. Due to the persistence of viral antigenic stimulation, biomarkers to use after the worsening progression of HCV infection to lymphoproliferative and/or autoimmune diseases are widely needed. Laboratory methods used to detect and characterize low concentrations of cryoprecipitates and immunotyping patterns could improve patient management. The most critical factor affecting cryoglobulin testing is that the pre-analytical phase is not fully completed at 37°C.

Serological profile of asymptomatic HCV positive patients with low level of cryoglobulins

Clinical spectrum of hepatitis C virus (HCV)-related cryoglobulinemia varies from an asymptomatic presentation to severe vasculitis and lymphoma. A recent study in HCV-negative patients suggests that low cryoglobulins (CGs) levels are responsible for severe renal and neurological complications. The aim of this study was to identify a panel of serological biomarkers associated with low levels of CGs in HCV-positive patients. We studied a population of 79 untreated patients with chronic HCV infection: 13 naïve patients without CGs; 28 patients with asymptomatic mixed cryoglobulinemia (MC) and low levels of CGs (16/28 with polyclonal type III and 12/28 with microheterogeneous type III CGs); 38 patients with symptomatic MC and high levels of type II CGs. Serum samples were collected and examined for rheumatoid factor (RF) IgG and IgM, free light chains (FLCs) and C3 and C4 complement components. We found that RF-IgG and IgM, free k chains and k+λ were increased while C4 component was reduced, both in symptomatic and asymptomatic patients. Our results suggest that, even in absence of MC symptoms, the low levels of CGs may represent a trigger of activation for immune system in course of HCV infection. The identification of a correlated biomarkers panel could improve the clinical management of these patients and pave the way for target treatment strategies. © 2018 BioFactors, 45(3):318-325, 2019.

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.

Cryoglobulin Test and Cryoglobulinemia Hepatitis C-Virus Related

Cryoglobulins are immunoglobulins that precipitate in serum at temperatures below 37°C and resolubilize upon warming. The clinical syndrome of cryoglobulinemia usually includes purpura, weakness, and arthralgia, but the underlying disease may also contribute other symptoms. Blood samples for cryoglobulin are collected, transported, clotted and spun at 37°C, before the precipitate is allowed to form when serum is stored at 4°C in a Wintrobe tube for at least seven days. The most critical and confounding factor affecting the cryoglobulin test is when the preanalytical phase is not fully completed at 37°C. The easiest way to quantify cryoglobulins is the cryocrit estimate. However, this approach has low accuracy and sensitivity. Furthermore, the precipitate should be resolubilized by warming to confirm that it is truly formed of cryoglobulins. The characterization of cryoglobulins requires the precipitate is several times washed, before performing immunofixation, a technique by which cryoglobulins can be classified depending on the characteristics of the detected immunoglobulins. These features imply a pathogenic role of these molecules which are consequently associated with a wide range of symptoms and manifestations. According to the Brouet classification, Cryoglobulins are grouped into three types by the immunochemical properties of immunoglobulins in the cryoprecipitate. The aim of this paper is to review the major aspects of cryoglobulinemia and the laboratory techniques used to detect and characterize cryoglobulins, taking into consideration the presence and consequences of cryoglobulinemia in Hepatitis C Virus (HCV) infection.