Not All Lupus With Nephritis Is Lupus Nephritis

A 56-year-old man with polyarthritis involving hands and wrists with hair loss, nonscarring alopecia, malar rash (Fig. 1), painless mouth sores, Antinuclear antibody 1:2560 homogeneous, positive dsDNA, and positive Smith antibody. The patient developed urinary abnormalities. Proteinuria was 1024 mg in 24 hours, and there were red cell casts. Glomerular filtration rate was 95 mL/min per 1.73 m2, and serum creatinine was 0.95 mg/dL. Renal biopsy revealed no evidence of lupus. There was IgA nephropathy and IgA immune complex deposition on immunofluorescence (Fig. 2), with low chronicity. There was no mesangial hypercellularity. PAS (periodic acid–Schiff) showed open loops, with smooth capillary membranes (Fig. 3). MEST-C (histologic scoring system for patients with IgA nephropathy) scores for M-O (mesangial proliferation), E-O (endocapillary hypercellularity), S- 1 (segmental glomerulosclerosis), T-1 (tubular atrophy, interstitial fibrosis), and C-O (crescent formation). Treatment included hydroxychloroquine, belimumab, and angiotensin-converting enzyme inhibitors.FIGURE 1: Sparing of nasal labial foldFIGURE 2: IgA immunofluorescence staining positiveFIGURE 3: No mesangial hypercellularity found in the glomerulusFour differential diagnoses are as follows: mesangial proliferative glomerular nephritis, focal proliferative glomerulonephritis, diffuse proliferative glomerulonephritis, membranous nephropathy