Granulomatosis with polyangiitis (GPA), formerly known as Wegener's granulomatosis, is a rare multisystem autoimmune disease of unknown etiology.
It's a rare and deadly form of vasculitis. Inflammation limits the flow of blood to important organs, causing damage. It can affect any organ, but it mainly affects the sinuses, nose, trachea, lungs, and kidneys.
The cause of GPA is unknown. It can affect people at any age. Men and women are equally affected. It's more common in whites.
GPA is extremely difficult to diagnose as its symptoms in the initial phase are not distinguishable from the symptoms of many other common diseases. Symptoms may include joint pain, weakness, tiredness, and cold symptoms such as a runny nose that doesn't get better, difficulty breathing, and chest pain. It's generally only diagnosed after many other common diseases have been ruled out.
Doctors use blood tests, chest X-rays, and biopsies to diagnose GPA and rule out other causes of the symptoms.
It's distinguished from other forms of vasculitis by the presence of granulomas. The most determinant blood test is the c-ANCA.
As such, because of its rarity and indistinguishable symptoms, it's considered one of the ultimate zebra diagnoses.
GPA is a frequent differential diagnosis on the show, but it only appeared at the end of Season 7, where it was almost mistaken for cancer. This was not a stretch as both conditions respond well to chemotherapy and the granulomas can be mistaken for tumors, particularly where they cannot be biopsied.
Until the widespread development of steroids and immunosuppressants, GPA was a virtual death sentence with most patients dying within a year of diagnosis. However, modern steroids and immunosuppressants can control the disease, although they cannot cure it. Most patients now live a normal lifespan, although they may suffer from flare-ups of symptoms from time to time.