# Recurrent coronary artery in-stent restenosis caused by metal allergy: a case report

## TL;DR

A woman repeatedly developed artery blockages after stent implantation due to a metal allergy, highlighting challenges in managing such cases.

## Contribution

This case report highlights the rare but significant role of metal allergy in recurrent in-stent restenosis despite varied treatment strategies.

## Key findings

- A nickel allergy was identified as the cause of recurrent in-stent restenosis after a nickel-rich stent.
- In-stent restenosis recurred even after switching to a platinum–chromium alloy stent and drug-coated balloon treatment.
- The case underscores the difficulty in managing ISR when caused by metal hypersensitivity.

## Abstract

This article describes the case of a middle-aged woman who developed recurrent in-stent restenosis (ISR) due to metal allergy. The first ISR occurred after implantation of a nickel-rich Medtronic Endeavor Resolute stent (35% nickel, 35% cobalt, and 20% chromium). A skin patch test revealed a strong nickel allergy (++), with no allergic reaction to cobalt. Nickel allergy was considered to be the cause of the first ISR. Then, a drug-coated balloon platinum–chromium alloy stent was implanted, and ISR occurred again during follow-up. The article discusses this special case and clinically relevant management options. This case highlights a scenario with refractory in-stent restenosis persisting despite various treatment strategies, including stents with different metal components, drug-coated balloons, and intensive drug therapy.