Marked elevation of procalcitonin level can lead to a misdiagnosis of anaphylactic shock as septic shock.

The case of a 74-year-old woman who presented with hyperthermia and hypotension is reported. Laboratory test results revealed marked elevation of C-reactive protein (CRP) and procalcitonin (PCT) levels. The clinical presentation and laboratory test results were suggestive of septic shock. No infectious focus was identified. The shock recurred after what was subsequently understood to be an unintended re-challenge with risedronate sodium. Drug-induced anaphylactic shock was finally diagnosed. Anaphylactic shock may be misdiagnosed as septic shock in patients who present with markedly elevated PCT levels.