Platypnea-orthodeoxia syndrome - a rare presentation and diagnostic challenge

Platypnea-orthodeoxia syndrome (POS) is a rare condition which presents with positional dyspnoea and deoxygenation on an orthopneic position which resolves when supine. We present a rare presentation of POS in a 75-year-old man, who initially presented with mixed symptomology including dyspnoea on exertion and syncope. He was found to have intermittent symptomatic hypoxia and initial investigations ruled out infection, pulmonary embolism and interstitial lung disease. Pulse oximetry confirmed positional variations in oxygenation. A transthoracic echocardiogram and a transoesophageal bubble echocardiogram with positional manoeuvres confirmed the presence of a large patent foramen ovale (PFO) with shunting. The patient was referred to the tertiary centre for PFO closure which resulted in resolution of his symptoms. This case report highlights the importance of recognising POS as a rare differential in causes of unexplained dyspnoea and utilising multiple imaging techniques to confirm the diagnosis.