IgG4-related disease is a fibro-inflammatory condition often, but not always, associated with elevated serum IgG4 concentrations. Grados et al.  reported that sFLC concentrations were significantly higher in IgG4-related disease than normal, and 43% of patients had abnormally high κ/λ sFLC ratios. This was independent of renal function, and the authors concluded that there was a disproportionate increase in κ FLC production. Patient numbers were too small (n=16) to assess any relationship with disease activity or prognosis.