Breathless at rest: a paradoxical platypnea-orthodeoxia syndrome variant

Platypnea-orthodeoxia syndrome (POS) is a rare and underdiagnosed clinical syndrome classically characterised by positional dyspnea (platypnea) and arterial oxygen desaturation (orthodeoxia) while upright, which improves in the supine position. There are no known cases of a POS variant where oxygenation improved during exercise and in the upright position, but worsened at rest and while supine. We present a novel case of a man in his mid-70s with symptoms and oxygen saturations paradoxical to classic POS, who was found to have a right-to-left shunt across a patent foramen ovale (PFO) with normal right atrial pressure (RAP), ascending aortic ectasia and concomitant right hemidiaphragm elevation without paralysis. On successful transcatheter PFO closure, no hypoxaemia was found in any position or exertional level. To that effect, this paradoxical variant may represent an under-recognised and underdiagnosed form of POS that warrants further investigation in patients with positional dyspnoea and hypoxaemia.