We report a rare case of spontaneous focal dissection and rupture of an atherosclerotic left subclavian artery causing haemothorax. A non-traumatic dissection and rupture at this location causing haemothorax is rare. Most haemothoraces are traumatic in nature with only a small number of natural causes [
1]. Natural causes of haemothorax are frequently due to acute rupture of major blood vessels, coagulopathy, rupture of lung adhesions and inflammatory conditions, or chronically from connective tissue disorder or malignant processes [
1,
2]. The source of haemothorax is frequently from a ruptured dissecting or aneurysmal aorta and rarely from other vessels [
2].
Atherosclerosis is by far the most common pathology reported in the left subclavian artery, but other relatively rarer pathologies including arteritis, inflammation due to radiation exposure, compression syndromes, fibromuscular dysplasia and neurofibromatosis have been reported [
3,
4]. In these conditions, there are only a small number of case reports reporting left subclavian rupture and are exclusively from underlying connective tissue disorder or vascular anomalies of the aortic arch [
5‐
7]. Other causes of rupture at this site include trauma or catheterisation [
7]. Although theoretically possible, atherosclerotic blood vessels with underlying hypertension can result in focal dissection and subsequent rupture of any artery. However, to the best of our knowledge there is no case reported on the left subclavian artery in forensic literature [
2,
6]. Of peculiar interest is that the focal distribution of the atherosclerosis isolating in the left subclavian artery with the aorta and other branches is almost unaffected. In this case, it is unclear why atherosclerosis was localised in the left subclavian artery and not the aorta nor in the right side. This may be related to higher turbulent and/or pulsatile blood flow into the left subclavian artery as previously hypothesised [
8]. This is evident in the atherosclerosis being proximal and near the orifice. This observation is also in keeping with the heterogenicity of atherosclerotic distribution in blood vessels observed in clinical literature [
9,
10]. Although rare, in non-traumatic causes of acute haemothorax where an aortic source is not evident, exploring the branches of the aorta (such as the left subclavian arteries, as presented in this case) and other major vessels may identify rare causes of haemothorax.