Pulmonary arterial hypertension is a syndrome—not a disease—and has a number of causes.¹ Included in these causes are a wide range of pathoaetiologies such as HIV infection, portopulmonary hypertension, intracardiac shunt, chronic thromboembolic disease, hypoxic lung disease, connective tissue disease, idiopathic pulmonary hypertension, and familial pulmonary hypertension associated with mutation of the BMPR2 gene.

In this issue of Thorax Jaïs et al² have examined the clinical background of 257 patients referred to their centre for treatment of chronic thromboembolic pulmonary hypertension (CTEPH). They found that 8.6% of the patients had a history of splenectomy compared with 2.5% of patients with idiopathic pulmonary hypertension (IPH) and 0.4% in the general population. They concluded that splenectomy alone had caused thromboembolism and hence the pulmonary hypertension in these patients. But is this true?

Chronic thromboembolic disease has been defined as “pulmonary hypertension caused by the absence of thrombus resolution after acute pulmonary embolism which has resulted in sustained obstruction of the pulmonary circulation”. This view is probably outdated because in 50% of cases there is no definite history of venous thrombosis and it is likely that many cases are a consequence of in situ thrombosis.³ Bonderman et al⁴ have recently looked at the medical conditions that increased the risk of CTEPH in 109 consecutive patients and found that splenectomy increased the relative risk of this condition by a factor of 13.

The findings of Jaïs et al² and Bonderman et al⁴ are not new—for example, …