Predominant tubulointerstitial lupus nephritis with preceding pernicious anemia

Predominant tubulointerstitial nephritis with negligible glomerular lesions is a rare form of lupus nephritis. Although tubulointerstitial changes occur in two-thirds of patients with lupus nephritis, these lesions were mostly accompanied by glomerulonephritis. Predominant tubulointerstitial lupus nephritis has been reported to be only 13 cases in the literature as far as we surveyed. Here, we present a case of a 72-year-old male who had pancytopenia associated with pernicious anemia and later developed a mild proteinuria and renal insufficiency. Although urinary tubulointerstitial markers increased, serological screening tests for tubulointerstitial nephritis were all negative. Three months later, the patient was diagnosed as systemic lupus erythematosus, based on polyarthritis, positive antinuclear antibody, immunological disorder and hematological disorder. Renal biopsy revealed severe infiltration of mononuclear cells in the interstitium with minimal abnormalities in glomeruli. Positive IgG and C1q staining with immunofluorescence antibody method in the tubular basement membrane and dense deposits in the same region with electron microscopy confirmed a diagnosis of predominant tubulointerstitial lupus nephritis. Since the patient's renal function declined rapidly, treatment with intravenous 500 mg methyl prednisolone followed by 40 mg/day of oral prednisolone was initiated. The patient's renal function improved and became stable even after tapering of prednisolone. Although lupus nephritis is generally accompanied by multiple symptoms such as fever, malaise, arthralgia, rashes, this case showed only pernicious anemia and tubulointerstitial nephritis initially.