What is a characteristic finding in patients with microscopic polyangiitis?

In patients with microscopic polyangiitis, a characteristic finding is raised serum creatinine. This is indicative of renal involvement, which is a common feature of this condition. Microscopic polyangiitis is a small-vessel vasculitis that frequently affects the kidneys, leading to glomerulonephritis and subsequent renal impairment. The elevated serum creatinine level serves as a marker of kidney function decline and is often seen in the clinical presentation of affected individuals.

The other options, while they may be relevant in different contexts, do not characterize microscopic polyangiitis specifically. For example, thrombocytopenia can occur in various conditions but is not a defining feature of this vasculitis. Increased eosinophils typically point toward eosinophilic conditions or allergic responses rather than microscopic polyangiitis. Elevated blood pressure can arise in many patients with kidney disease but is also not a specific marker for microscopic polyangiitis. Therefore, the most telling marker in the context of this condition is raised serum creatinine, reflecting the underlying renal pathology.