IGG4 Related Disease

Clinical features

• 9% proteinuria
• 67% have elevated IgG4
• 50% have hypocomplementemia
• 30% eosinophilia
• ANA 30%

Renal Biopsy

TIN picture

60% of biopsy’s have AKI or CKD

• dense lymphoplasmocytic infiltrate
• storiform fibrosis
• Plasma cell rich interstitial infiltrates
• Eosinophils common
• Expansile interstitial fibrosis, storiform
• Increased igG4 plasma cells = > 10 cells/field TBM deposits
• 70-80% have IgG4 BTM deposits: IgG/ K/L , C3, C1a
• This is odd in other types of TIN

Glomerular disease phenotypes exist: MN, IGAN, MCD, MPGN

• ~7% of IgG4 TIN have coexisting MN. Proteinuria: common, heavy (mean 8g). neg for MN abx

Note primary membranous is also igG4 dominant

Treatment

• 90% response to steroids first line, ritux is alternative. Takes 2-4 weeks of steroids typically.
• High relapse rate (risk factors : high serum igG4, serum igE, circulating eosinophils)
• 70% relapse post ritux
• Watch carefully, most common gland for recurrance is lung and lacrimal
• Can track the lymphocytes subsets. Alternative approach might be 2-3 years of 6 monthly treatment and hope the best.
• No current role for tracking IgG4 levels