Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (27 page)

   Positive RF (low titers), negative ANA, and mild hypergammaglobulinemia, especially of the IgA class, are frequently found in GPA.

   Urinalysis and serum creatinine measurements reflect the degree of renal involvement. Microscopic hematuria and proteinuria are common.

   Elevated CRP and ESR.

   Mild normochromic, normocytic anemia is present in nearly half of the patients.

   Diagnosis must be confirmed by biopsy of the pulmonary (highest yield), upper airway, or renal tissue.

HENOCH-SCHÖNLEIN PURPURA

   See Chapter
3
, Cardiovascular Disorders; see also Henoch-Schönlein Purpura Nephritis in Chapter
12
, Renal Disorders.

   See Table
2-1
.

HYPERSENSITIVITY VASCULITIS

   Definition

   Hypersensitivity vasculitis (HS) is a vasculitis of small vessels of the skin, which can be idiopathic or secondary to drug treatment or infections.

   See Table
2-1
.

   Who Should Be Suspected?

   HS patients present with skin lesions, palpable purpura, and/or petechiae that might follow the initiation of drug therapy or infection (e.g., hepatitis C infection with cryoglobulinemia). Other findings include fever, urticaria, and arthralgia.

   Visceral organ involvement is uncommon.