Pulmonary arterial hypertension is a relatively rare, but very serious complication of HIV infection. It is casued by the blood pressure rising in the arteries carrying oxygen-deprived blood away from the heart to be replenished in the lungs.

Pulmonary arterial hypertension can be inherited but can also be associated with other conditions including HIV infection. HIV causes the pulmonary arteries to become thickened and narrowed, leading to the rise in pressure, but the mechanisms for this is unknown. The condition is seen in all groups of people with HIV infection, irrespective of the cause of infection or the degree of immunodefiency.

In the mid 1990s, before the advent of triple combination antiretroviral therapy it was estimated that the prevalence of the condition in patients with HIV was one in 200 patients. This is much higher than the incidence in the general population, where there are one or two cases per million. However, a recent French study of almost 7650 HIV-positive patients has found that it is no less common now than it was before antiretroviral therapy was introduced, with a prevalence of 0.5%^[1].

It is also a much more serious disease in HIV infection: according to a Spanish study published in 2003,  just over half the individuals who developed the condition died within three years^[2].