# A Curious Case of Purple Chromaturia

## TL;DR

A patient treated with hydroxocobalamin after a house fire developed purple urine, a harmless but confusing side effect that resolved on its own.

## Contribution

This case highlights hydroxocobalamin-induced chromaturia as a benign, self-limiting side effect that can mimic serious conditions.

## Key findings

- Purple chromaturia occurred in a patient treated with hydroxocobalamin after smoke inhalation.
- No evidence of hematuria, hemolysis, or renal impairment was found.
- The discoloration resolved spontaneously over five weeks without intervention.

## Abstract

Hydroxocobalamin, an antidote for cyanide toxicity, is known for its safety and efficacy. A notable side effect is dark red to purple chromaturia, sometimes mimicking hematuria. We report the case of a middle-aged female exposed to smoke inhalation following a house fire, who was treated on-site by emergency medical services with oxygenation and intravenous hydroxocobalamin and developed purple urine shortly after admission. Hematuria, hemolysis, rhabdomyolysis, and renal impairment were excluded with appropriate workup. The discoloration resolved spontaneously over five weeks without intervention, consistent with hydroxocobalamin-induced chromaturia. While benign and self-limiting, this phenomenon may cause diagnostic confusion and patient concern. Awareness of this side effect can prevent unnecessary investigations and reassure patients about its transient nature.