IgG cryoglobulinemia.

Area of Science:

• Immunology
• Virology
• Neurology

Background:

• Mixed Cryoglobulinemia (MC) is a significant extrahepatic manifestation associated with Hepatitis C Virus (HCV).
• MC is characterized as an autoimmune and B-lymphoproliferative disorder.
• Cryoglobulins (CGs) are classified into types based on immunoglobulin (Ig) composition, with Types II and III involving immune complexes with rheumatoid factor activity.

Purpose of the Study:

• To investigate the role of specific IgG subclasses in the early stages of Hepatitis C Virus-associated Mixed Cryoglobulinemia.
• To explore the association between IgG subclasses, rheumatoid factor activity, and neurological complications in HCV-positive patients.

Main Methods:

• Case series analysis of six Hepatitis C Virus-positive patients presenting with peripheral neuropathy and transient ischemic attacks.
• Cryoprecipitate analysis using immunofixation electrophoresis to determine IgG subclass composition (IgG1, IgG2, IgG3, IgG4).

Main Results:

• All six patients exhibited cryoprecipitates composed of IgG1 and IgG3 subclasses with probable rheumatoid factor activity.
• One patient presented with monoclonal IgG3 in their cerebrospinal fluid.
• The findings support the hypothesis of IgG3 involvement in the initiation of CGs.

Conclusions:

• The presence of IgG1 and IgG3 subclasses is a key immunochemical feature in this cohort of HCV-associated MC patients.
• Hypothesizes that IgG passage across the blood-brain barrier, involving these subclasses, may contribute to transient ischemic attacks (TIAs) via intrathecal immune complex precipitation.