Understanding PAH  What is Pulmonary Arterial Hypertension
(PAH)?  PAH is a disease in which the pressure in a patient's
pulmonary arteries becomes dangerously high. Pulmonary arteries
carry blood that has returned from the body to the lungs, where
the blood receives a fresh supply of oxygen. That high blood
pressure puts a strain on the heart.  PAH is one of five types
of pulmonary hypertension (PH).  PAH worsens over time and is
life-threatening. It is a relatively rare disease, affecting 1
in 100,000 to 1 in 1 million people.  There are several types of
PAH:  Idiopathic (IPAH)—PAH in which the cause is unknown
Familial (FPAH)—PAH that runs in families and often is linked to
a genetic defect  Associated (APAH)—the most common type of PAH,
which is caused by or occurs at the same time as other medical
conditions, including:    • Collagen vascular disease (or
connective tissue disease)--includes autoimmune diseases such as
scleroderma or lupus; in autoimmune diseases, the body's immune
system mistakenly atta