Lupus nephritis and systemic disease: Case

This girl has systemic lupus erythematosus with active proliferative lupus nephritis. The diagnosis rests on the multisystem clinical picture (malar rash sparing the nasolabial folds, oral ulcers, symmetrical arthritis), the active urinary sediment (haematuria with dysmorphic red cells and red cell casts, proteinuria), mild renal impairment, and the serological signature of active lupus (positive antinuclear antibody, strongly positive anti-dsDNA, and low complement C3 and C4). The combination of an active sediment with falling complement and high-titre anti-dsDNA is the serological signature of proliferative Class III or IV disease, which a renal biopsy would confirm. ^[1]

Clinical findings

The pattern is unequivocally that of proliferative lupus nephritis. The systemic features of lupus (malar rash, oral ulcers, arthritis) accompany the renal presentation, which is the common adolescent scenario. The active urinary sediment with dysmorphic red cells and red cell casts reflects the endocapillary inflammation and basement membrane disruption of proliferative disease. The proteinuria (urinalysis 2 plus, confirmed quantitatively) reflects the loss of the filtration barrier integrity. The mild renal impairment (creatinine of 98, slightly elevated for a 13-year-old) reflects the reduction in glomerular filtration from the proliferative and crescentic lesions. The hypertension (140 over 90, above the 95th centile for age) is driven by the inflammatory and ischaemic injury to the glomerulus and the renin-mediated vasoconstriction that follows. ^[1]

The serology confirms active immune-complex disease. The low C3 (0.42) and low C4 (0.07) reflect consumption of both components through classical complement pathway activation by the glomerular immune complexes, which distinguishes lupus from post-infectious glomerulonephritis where only C3 falls. The strongly positive anti-dsDNA (350 IU per mL) is the antibody that forms the nephritogenic immune complexes and correlates with disease activity and nephritis. The homogeneous antinuclear antibody pattern is consistent with lupus. ^[1]