[Interstitial lupus nephritis]

A 17-year old-male presented with a 6-week history of weight loss, lassitude and calf pains. On examination he was very pale. Laboratory tests showed a very high erythrocyte sedimentation rate (155 mm in the first hour), anaemia (haemoglobin 10.1 g/dl), and a raised serum creatinine of 1.54 mg/dl. Microhaematuria (5-10 erythrocytes/microliter) and pronounced pyuria (500 leucocytes/microliter) were present, but the urine was sterile and there was no increase in albumin excretion. The serum IgG was raised to 75.7 g/l, suggesting an autoimmune disorder. Anti-nuclear antibodies (titre 1 : 1920) and anti-double-stranded DNA antibodies (31 U/ml) were present, while the serum complement C4 was decreased to 0.11 g/l. Renal histology showed an interstitial nephritis without glomerular involvement, while the bone marrow showed vasculitis accompanied by a prominent plasma-cell infiltrate. A diagnosis of interstitial nephritis associated with systemic lupus erythematosus was made, with asymptomatic cardiac and hepatic involvement. Renal function recovered rapidly with prednisolone therapy (initial dose 2 mg/kg.d). While glomerulonephritis is the most common lupus-associated renal disorder, isolated interstitial nephritis may occur in some cases, often with an absence of proteinuria.