The response to hypoxia of both the systemic and pulmonary circulation is dependent on oxygen sensing and subsequent adaptations. These adaptations are, at least in part, mediated by several oxygen-dependent transcription factors that can initiate changes in gene expression. The hypoxia-inducible factor-1 (HIF-1) is believed to be the main transcription factor responsible for the responses and acclimatization to hypoxia, and certainly in the case of pulmonary hypertension does this transcription factor play an important role. As will be summarized in the present review, this has been demonstrated both on a molecular level, in animal models and in human populations.

Pulmonary hypertension in schistosomiasis is a topic which has recently attracted renewed attention. Schistosomiasis is endemic in 74 countries, with the greatest burden in sub-Saharan Africa. Pulmonary hypertension is a serious complication of infection for which the prevalence is unclear. Few systematic reviews have attempted to collate and evaluate the evidence behind this issue. A thorough search of the literature was performed and studies assessing prevalence were retrieved and analyzed against a quality assessment score. A total of 38 studies were identified of which 28 were retrieved for assessment. Due to poor epidemiological methods, none of the studies identified met the review's initial inclusion criteria. There has been an increase in the number of studies over recent years, with better use of invasive methods to detect pulmonary hypertension. However, the majority of these are hospital-based studies, many are from Brazil, most have small sample sizes and there is much variation in the definition of pulmonary vascular disease used. Pulmonary hypertension in schistosomiasis is likely to cause a substantial burden of disease and is potentially the leading cause of pulmonary hypertension worldwide. However, good quality studies with large community samples from sub-Saharan Africa are desperately needed in order to accurately estimate the number of people affected globally.