Glomerulonephritis, Cryoglobulin-Associated

Key Features

• Essential (mixed) cryoglobulinemia is a vasculitis caused by cold-precipitable immunoglobulins (cryoglobulins)

• Causes

  • Hepatitis C infection (usual)

    • Clonal expansion of B lymphocytes produces IgM rheumatoid factor

    • Immune complexes form from rheumatoid factor, hepatitis C viral antigen, and polyclonal anti-hepatitis C viral IgG

  • Other overt or occult infections

  • Viral, bacterial, and fungal infections

  • Some autoimmune diseases and lymphoproliferative disorders

Clinical Findings

• Purpuric and necrotizing skin lesions in dependent areas

• Arthralgias

• Fever

• Hepatosplenomegaly

Diagnosis

• Serum complement levels are low

• Rheumatoid factor often elevated

• Kidney biopsy: crescent formation, glomerular capillary thrombi, membranoproliferative glomerulonephritis (MPGN)

Treatment

• Aggressive targeting of the causative infection

• Pulse corticosteroids, plasma exchange, rituximab, and cytotoxic agents have been used when

  • There is little risk of exacerbating the underlying infection

  • No infection is present