Hypocomplementemic interstitial nephritis with long-term follow-up

Prednisone-sensitive hypocomplementemia, renal insufficiency, and kidney biopsy demonstrating severe tubulointerstitial nephritis (TIN), storiform fibrosis, and tubulointerstitial immune deposits are typical of IgG4-related tubulointerstitial nephritis and hypocomplementemic interstitial nephritis. A diagnosis of hypocomplementemic interstitial nephritis requires clinical and pathologic exclusion of IgG4-related tubulointerstitial nephritis. We describe a patient with hypocomplementemic interstitial nephritis who did not develop diagnostic features of IgG4 related disease (RD) over 2-year follow-up. We conclude that hypocomplementemic interstitial nephritis could be on a biologic spectrum with IgG4-related disease, but not all cases will develop the abundance of IgG4-positive plasma cells, systemic manifestations, or elevated immunoglobulin levels characteristic of IgG4-RD