'Too much of a coincidence': identical twins with exertional heatstroke in the same race.

This report discusses a unique case of monozygotic male twins who both collapsed with exertional heat stroke (EHS) during the same marathon in relatively cool conditions. The twins were official race pacers in a popular city marathon held in the early spring in the UK. Both recovered uneventfully due to the prompt recognition of EHS and use of aggressive cooling measures, which prevented life-threatening complications. The case illustrates that EHS is a complex illness with a possible genetic predisposition, which can occur among runners even in cooler conditions. This link is explored together with the influence of their role as race pacers and the additional backpack worn in the development of EHS. 2016 BMJ Publishing Group Ltd.