A โSyndromeโ is a collection of symptoms of conditions which we suspect means something, but canโt really prove it.ย Itโs contrasted to a โDisease,โ which has a definite way of being proved.ย So for example, people with โIrritable Bowel Syndromeโ (IBS) may have abdominal pain, constipation, and/or diarrhea, which can be bothersome or even disabling, but thereโs no way to prove exactly what is happening in the body, because all tests are normal.ย โInflammatory Bowel Diseaseโ (IBD), however, causes ulcers in the bowel, can be definitively identified by biopsy, and if severe, can require removal of part or even the entire bowel.ย Occasionally people can die from IBD, never from IBS.
โAcquired Immunodeficiency Syndromeโ (AIDS) is also a โsyndrome,โ and people certainly can die from it.ย The reason itโs called โsyndromeโ instead of โdiseaseโ was that when first recognized in 1981, all we knew was that some people were suddenly developing a wide variety of fatal infections that had previously been extremely rare.ย They were caused by โopportunisticโ germs that are so weak that they never caused illness.ย All of use have them in us, but almost nobody ever gets sick because our immune system controls them โ unless, of course, the immune system weakens for some reason.ย
So the term โAIDSโ was applied to anyone with โopportunistic infections,โ meaning for some reason, they had lost their immune systems.ย But we didnโt know why, so we couldnโt say it was a โdisease.โย Then, when a previously-unknown virus was found to be responsible, it was named โHuman Immunodeficiency Virusโ (HIV), and we do speak of โHIV Diseaseโ (though just say โHIVโ for short).ย Really, AIDS is nothing more than end-stage untreated HIV infection, but we still use the term.ย By the way, the โAโ which stands for โAcquiredโ is because thereโve always been rare immunodeficiency diseases babies are born with; theyโre โcongenitalโ instead of โacquired.โ
So back to the term โsyndrome,โ โ syndromes are certainly illnesses, but ones which canโt be precisely defined by biopsies, x-rays, blood tests, or anything. IBS is thought due to disturbances in the rhythm of the bowel, but nobody can prove it. Maybe someday they will.