Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (561 page)

   HSP, also termed IgA vasculitis, involves hypersensitivity systemic vasculitis of small vessels with deposition of IgA-containing immune complexes. It mainly affects the skin as well as other organs such as the kidneys, digestive tract, and joints. This condition can occur at any time in life, but most common in children.

   Kidney damage is the most common long-term complication of HSP. It is more frequent and tends to be more severe in adults than children. Renal involvement is typically noted shortly after the onset of systemic symptoms. Up to 30% of adults will experience CKD or kidney failure within 15 years after diagnosis.

   Diagnosis is mainly clinical.

   Laboratory Findings

   Hematuria and proteinuria are present in approximately one third of patients and usually associated with decreased GFR. Nephrotic-range proteinuria is more likely to be seen in adults than children.

   Elevated serum levels of IgA and IgA-containing immune complexes.

   Renal biopsy supports the diagnosis and assesses severity of the disease. Biopsy results are identical to those found in IgA nephropathy.

LUPUS NEPHRITIS

   Overview

   See systemic lupus erythematosus (SLE).

   Up to 60% of patients with SLE are diagnosed with lupus nephritis (LN). The prevalence is significantly higher in blacks and Hispanics than in whites, and higher in men than women. The International Society of Nephrology/Renal Pathology Society classification divides LN into six classes (I–VI) based on kidney biopsy histopathology.

   Laboratory Findings

Depend on the class of LN:

   Minimal mesangial LN (class I): patients have normal urinalysis and serum creatinine concentration.

   Mesangial proliferative LN (class II): microscopic hematuria and mild proteinuria may be present.