[Lupus nephritis with crystal structures in glomerulopathy ]

Lupus nephritis is a common phenomenon in Systemic Lupus Erythematosus (SLE). We analyzed a renal biopsy of a 30-year-old woman with SLE. The clinical history showed a typical SLE with generalized symptoms without demonstrable lupus coagulant, positive for anti-nuclear antibodies and anti-ds-DNA antibodies but negative for rheumatoid factor, cryoglobulins and antiphospholipid antibodies. A paraproteinemia for IgA, IgG and IgM was not detectable. Using light, electron and immunoelectron microscopy electron-dense deposits were noted in subepithelial, subendothelial and mesangial position. Most remarkably, the electron-dense deposits and mesangial areas in the vicinity of deposits contained an electron-dense crystalline material. The crystalline structures were composed of IgG and kappa light chains, while they were negative for IgM, IgA and lambda light chains, as demonstrated by immunoelectron microscopy. As far as we know, this is the first case of lupus nephritis with crystalline structures. Since we could not detect cryoglobulinemia or paraproteinemia, other mechanisms possibly favor organization of macromolecular structures.