Lupus nephritis with cryoglobulinemic glomerulonephritis features: a diagnostic conundrum.

In this clinical case, we report an atypical and unique presentation of systemic lupus erythematosus (SLE) in a 39-year-old female with nephrotic syndrome. The patient exhibited class IV plus V lupus nephritis and extensive immune complex deposition within the intracapillary and arteriolar regions suggestive of cryoglobulinemic glomerulonephritis, despite no detectable circulating cryoglobulins. Electron microscopy revealed cryoglobulin-like deposit distribution in all glomerular examined compartments, namely subendothelial, intramembranous, subepithelial, and mesangial, apparently extending from the capillary hyaline thrombi. The case highlights the possibility of severe renal injury in SLE without circulating cryoglobulins and the diverse kidney manifestations associated with the disease. However, the impact on patient outcome was minimal, as classical treatment (id est National Institute of Health regimen) remained effective.