Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (562 page)

   Focal LN (class III): involves <50% of glomeruli and can be subdivided into subclasses depending on the activity/chronicity of the lesions. It is characterized by hematuria and proteinuria. In some patients, proteinuria may be in the nephrotic range and serum creatinine may be elevated.

   Diffuse LN (class IV): divided into subclasses similar to class III. Hematuria and proteinuria are present. Some patients may display nephrotic-range proteinuria and hypertension.

   Membranous LN (class V): most patients have nephrotic syndrome.

   Advanced sclerosing LN (class VI): characterized by sclerosis involving more than 90% of glomeruli.

   Titers of anti-DNA antibodies are elevated, and levels of C3 and C4 are low.

   Kidney biopsy is performed to establish the diagnosis and classify LN.

Suggested Reading

Hahn BH, McMahon MA, Wilkinson A, et al. American College of Rheumatology guidelines for screening, treatment, and management of lupus nephritis.
Arthritis Care Res.
2012;64(6):797–808.
http://www.rheumatology.org/practice/clinical/guidelines/Lupus_Nephritis_Guidelines_Manuscript.pdf

MYELOMA KIDNEY

   Overview

   See plasma cell myeloma.

   Myeloma kidney, or myeloma cast nephropathy, is a common complication of plasma cell myeloma in which monoclonal light chain (Bence Jones [BJ] proteins) excretion in the urine contributes to acute or chronic renal failure. Less frequently, high levels of free light chains can lead to immunoglobulin light chain amyloidosis or light chain deposition disease. These conditions are usually associated with insidious progression of renal failure rather than acute kidney injury.

   Laboratory Findings

   Increased urinary excretion of light chains (>100 mg/day but can be much higher; normal <30 mg/day). Bence Jones proteinuria is not detectable by urine dipstick and occurs in <50% of myeloma patients but in almost all patients with renal failure due to myeloma kidney. Kidney damage can also lead to albuminuria and azotemia.

   Protein electrophoresis and immunofixation of serum and a 24-hour urine collection help establish the diagnosis and determine the type and amount of monoclonal protein and light chains.