Renal disease
A 45-year-old man has experienced increasing malaise, nausea, and reduced urine output for the past 3 days. On physical examination, he is afebrile and normotensive. Laboratory findings show a serum creatinine level of 7.5 mg/dL. Urinalysis shows hematuria, but no pyuria or glucosuria. A renal biopsy is done; the light microscopic picture is shown in the figure. Which of the following additional studies is most useful for classification and treatment of this disease? A. Antinuclear antibody B. Anti–glomerular basement membrane antibody C. HIV-1 RNA copy level D. Quantitative serum immunoglobulins E. Rheumatoid factor F Urine immunoelectrophoresis —�—�—�—�—�—�— . The figure shows glomeruli with epithelial crescents indicative of a rapidly progressive glomerulonephritis. Crescentic GN is divided into three groups on the basis of immunofluorescence: type I (anti–glomerular basement membrane [GBM] disease); type II (immune complex disease); and type III (characterized by the absence of anti-GBM antibodies or immune complexes). Each type has a different cause and treatment. The presence of anti-GBM antibodies suggests Goodpasture syndrome; patients with this disorder require plasmapheresis. Type II crescentic GN can occur in systemic lupus erythematosus, in Henoch-Schönlein purpura, and after infections. Causes of type III crescentic GN include granulomatosis with polyangiits (ANCA-associated vasculitis) and microscopic polyangiitis. A positive ANA test result may be reported in patients with lupus nephritis, which uncommonly manifests with glomerular crescents. HIV nephropathy has features similar to those of focal segmental glomerulosclerosis (FSGS), which is not rapidly progressive. Quantitative serum immunoglobulins are not helpful because the important consideration is the pattern of immune deposits in the kidney. Rheumatoid factor is present in rheumatoid arthritis, which is not typically associated with renal complications. Urine immunoelectrophoresis is useful in categorizing a monoclonal gammopathy.
