OnExamination SCE in Respiratory Medicine (Updated Feb 2023)

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Demo Question A 68-year-old retired former banker comes to see you for breathing difficulties at both rest and exertion, developing over several years. When examining him you notice his breathlessness markedly decreases when he lies supine for your examination. Which of the following could be an underlying cause of his breathlessness?  

Guillain Barre Syndrome  Langerhans cell histiocytosis  Mesothelioma  Alpha-1-antitrypsin deficiency  Ventricular septal defect Key Learning Point Lower lobe predominant lung disease is a cause of breathlessness which improves on lying down (platypnoea). Other causes include Atrial Septal defect, Arterio-venous malformations, Cirrhosis, Autonomic failure and Supraglottic tumour. Explanation This man complains of breathlessness which improves when he lies flat.

The reason, in this case, is due to an intra-pulmonary shunt. Alpha 1 AT deficiency is a lower lobe predominant disease which means that when standing, the blood gravitates towards the affected lower lobes resulting in poor gas exchange due to a ventilation-perfusion mismatch. On lying flat, the pulmonary circulation is not affected by gravity as much and is able to circulate and exchange gases within the mid and upper lobes of the lung to a greater extent, reducing the ventilation-perfusion mismatch. Alpha-1-antitrypsin deficiency is the correct answer as it explains the breathlessness on lying down most completely.

Guillain barre can cause breathlessness which is relieved by lying down due to autonomic failure but the history is too long. Langerhans cell histiocytosis typically has an upper lobe predominance meaning symptoms would improve on standing up compared to lying down. Mesothelioma is a cause of breathlessness due to pleural effusions but this would not improve with lying down. Ventricular septal defects can cause severe breathlessness, but it is actually atrial septal defects that can vary (and improve) with lying down.