Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (539 page)

   Malignant nephrosclerosis: hematuria, azotemia, and proteinuria (minimal or marked).

   Renal biopsy is rarely indicated; diagnosis is mainly based on the clinical features.

IgA NEPHROPATHY

   Definition

   This immune-mediated condition, also referred to as Berger disease, is the most common cause of glomerulonephritis and the primary chronic glomerular disease worldwide. It is characterized by prominent deposition of IgA in the glomerular mesangium.

   Progressive decline in renal function occurs in approximately 40% of cases; half of these reach ESRD in 5–25 years. Up to 30% of cases have a benign course with persistent microscopic hematuria.

   Who Should Be Suspected?

   Presenting conditions may include persistent or intermittent hematuria (visible or microscopic) that can be associated with proteinuria. Episodes of visible hematuria occur in 75% of children and young adult cases and often start few days following upper respiratory infection.

   Few cases (<10%) can have a more severe presentation that is similar to nephrotic syndrome or rapidly progressive GN (edema, renal insufficiency, and hematuria).

   IgA deposits are frequently associated with Henoch-Schönlein purpura (IgA vasculitis) and may also be found with diseases of the GI tract (e.g., celiac disease), skin (e.g., dermatitis herpetiformis), liver (e.g., cirrhosis), carcinomas (e.g., lung, pancreas), autoimmune diseases (e.g., SLE, RA), and infections (e.g., HIV, leprosy).

   Laboratory Findings

   Diagnosis is based on renal biopsy finding by immunofluorescence microscopy showing predominant mesangial IgA deposits alone or with IgG, IgM, or both. Complement C3 and properdin are almost always present, and C1q is usually absent.

   Urinalysis shows RBCs and RBC urinary casts.

   Proteinuria is usually <2 g/day.