Rare diseases bullet 5: Primary pulmonary hypertension

Primary pulmonary hypertension (PPH) is a rare disorder with an incidence of one to two cases per million people per year in Western populations. It is a progressive disease usually affecting the arterial side of the pulmonary circulation and, if untreated, progresses to severe pulmonary hypertension and, finally, right heart failure. Characteristically, and because of the vague nature of the symptoms, PPH may take up to 18 months to diagnose and, following diagnosis, the median survival is under two years. The disease is most common in women (ratio 1.7:1) and the mean age at the time of diagnosis is in the mid 30s. This bleak picture of PPH has been transformed over the last decade, partly because of better diagnostic techniques allowing earlier diagnosis and also because of new treatments, in particular the use of continuous intravenous prostacyclin. It is now realised that vasoconstriction of the pulmonary vascular bed is not the primary cause of PPH but occurs in association with marked histological changes. These histological changes are seen not only in PPH but also in severe pulmonary hypertension in association with other disorders such as HIV infection, connective tissue disease, and the use of appetite suppressant drugs. The realisation that primary or unexplained pulmonary hypertension was the end of a spectrum of several diseases causing severe pulmonary hypertension has lent a new impetus to the understanding of the disease and prompted a major symposium sponsored by the World Health Organisation held in Evian, France, in September 1998. At this symposium were gathered clinical scientists from all over the world with an interest in pulmonary hypertension and the result was a consensus about classification of pulmonary hypertension, the pathobiological methods of screening, risk assessment, and treatment. The first part of this review considers the clinical aspects of pulmonary hypertension, in …