Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (25 page)

   Proteinuria and microscopic hematuria can be present.

GIANT CELL ARTERITIS

   Definition

   Giant cell (temporal) arteritis is a chronic systemic vasculitis of the large- and medium-sized vessels, involving especially the cranial branches of the arteries that originate from the aortic arch.

   Visual impairment is a major complication of the disease, and failure to make the diagnosis may lead to irreversible visual loss.

   See Table
2-1
.

   Who Should Be Suspected?

   Candidates are patients with severe bitemporal headache, visual disturbances (primarily partial, transient monocular visual loss), jaw claudication, and symptoms of polymyalgia rheumatica (30–50% of cases). Other frequent manifestations of systemic inflammation can be present and they include fatigue, general malaise, fever, anorexia, weight loss, and night sweats.

   This disorder mainly affects individuals >50 years or age and is extremely rare in younger people. The incidence rises markedly with increasing age, peaking in the eighth decade of life.

   Laboratory Findings

Diagnosis is mainly clinical. Laboratory studies are pertinent, but not specific.

   Increased ESR (≥50 mm/h, mean 88 mm/h).

   Thrombocytosis with platelet counts >400,000/μL and CRP levels >2.45 mg/dL have been found to be to the strongest laboratory predictors of a positive temporal artery biopsy.

   Increased levels of IgG and complement.

   Mild to moderate normocytic, normochromic anemia in approximately 50% of patients.