Schistosomiasis is endemic in more than 70 countries, affecting about 200 million people worldwide, of whom 80 percent are in sub-Saharan Africa. It is the leading cause of pulmonary arterial hypertension in the Global South. There are also pockets of infection in northeastern Brazil, near the Yangtze River in China, and in southeast Asia and the Middle East.

After infection, the schistosoma worm usually resides in humans and animals in targeted organs: the liver and the gastrointestinal tract for schistosoma mansoni or schistosoma japonicum, and the urinary tract for schistosoma haematobium.

The worms may reside there for 30 years or more, and both male and female worms excrete eggs. The adult worms do not cause disease, but the eggs they release are highly antigenic (toxic) and the cause of disease. The eggs will produce pathological changes, mainly complex inflammatory lesions called granuloma which lead to scarring.

Some of the eggs may escape from where the adult worms are and migrate to other tissues, particularly to the lung. The inflammation caused by the eggs causes changes in the blood vessels that leads to pulmonary arterial hypertension.

Diagnosing schistosomiasis-associated PAH

Patients with schistosomiasis-associated PAH may have no symptoms. Others with more extensive changes have symptoms that are the same as other forms of PAH.

The diagnosis of schistosomias-isassociated PAH is similar to other types of PAH. Studies are done to rule out other causes of the disease, and for persons from areas where infection is common, specific tests for schistosomiasis are needed.

Diagnosing Pulmonary Hypertension

Treating PAH

It is important to treat active schistosomiasis infection if present. This may help to decrease the inflammation and possibly prevent further worsening of the PH.

Reported treatment has included PDE5 inhibitors, endothelial receptor antagonists, or a combination of both therapies with improvement in six-minute walk distance.

The prognosis of schistosomiasis-associated PAH is not well understood and is likely very similar to that of idiopathic PAH.