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On Monday, Hollywood lost an iconic filmmaker to a debilitating disease.

Harold Ramis, the man behind numerous blockbuster films such as Ghostbusters and Groundhog’s Day, passed away at the age of 69 from complications relating to vasculitis.

Vasculitis is a blanket term for a diverse group of disorders that all share one common trait: inflammation of the blood vessels.  This inflammation can result in the total blockage or narrowing of the blood vessels, and can also cause an aneurism – or a ballooning of an artery.

Depending on which of these three situations occurs, vasculitis can manifest in very different ways.

“If you have an aneurism and it ruptures, then you can bleed internally,” Dr. Sahil Parikh, a cardiologist and vascular specialist at UH Case Medical Center in Cleveland, Ohio, told FoxNews.com. Parikh did not treat Ramis. “If you have a blockage, you can cut off the blood supply to a vital organ. And whichever organ is affected will depict the manifestation. If it happens in the brain, you can have a stroke; if it happens in the heart, you have a heart attack.”

According to a report from the Chicago Tribune, an infection Ramis suffered in 2010 likely triggered his autoimmune inflammatory vasculitis – meaning his overactive immune system led to the inflammation of his blood vessels.  The condition was so incapacitating, he had to relearn how to walk.  Then, in late 2011, Ramis had a relapse of the disease – and never fully recovered.

Parikh noted that vasculitis can sometimes be triggered by allergic reactions to medicines or certain infections, such as hepatitis B and C.  Additionally, vasculitis can be part of other rheumatic diseases, including lupus, arthritis or Sjögren's syndrome. But overall, health experts still do not know why some people contract certain forms of vasculitis and others do not.

“There really aren’t risk factors…and that’s the challenge. It’s a diagnosis that occurs to patients almost without reason,” Parikh said.  “There are certain predispositions, but Mr. Ramis is an older man, and many of these diseases occur in younger women, so it all depends on which kind of vasculitis it is.”

Just as vasculitis manifests differently depending on its location in the body, symptoms for the condition vary widely as well.  Vasculitis of the skin can result in red bumps, hives and itchy rashes, while vasculitis of the lungs can lead to shortness of breath. If patients experience abdominal pain, it could be related to a narrowing of arteries to the intestines, and severe headaches could indicate a narrowing of the temporal artery in the head.

Since symptoms for vasculitis can be so dissimilar, patients are often diagnosed with the condition long after its onset.  The most common tests for diagnosis include conducting a series of blood tests, doing a biopsy of blood vessel tissue, or performing an angiography – an X-ray that reveals blood flow through the vessels.

Once a biopsy confirms the disorder’s presence, physicians categorize vasculitis into one of three categories depending on the size of the artery involved:  small-vessel, medium-vessel and large-vessel.  This helps them to determine the best form of treatment – which can also be highly variable.

“The treatment for all of these diseases is pretty much suppression of the immune system, which typically involve steroid medications or more potent immunosuppressant drugs,” Parikh said. “But it totally depends on which [vasculitis] you have.  If it’s one related to an infection and you eradicate the infection, patients do well.  Meanwhile, others respond well to steroids, and others do not.  There isn’t a one-size-fits-all.”

Since vasculitis can be so unpredictable, Parikh said patients should speak to a doctor as soon as they start to experience painful symptoms – especially painful rashes or poor circulation to the extremities.  Parikh noted that just like any other disease, early detection ensures a better outcome.

“It’s a rare and very difficult condition to diagnose and treat, and the best way to treat  is to make a diagnosis,” Parikh said. “So patients should see a doctor if they are having pain.”