The crowd will tell have him running around getting tested for everything from celiac to Grave's disease. When the tests turn up negative, the crowd will claim that the testing threshold is wrong, or that doctors just can't be trusted. He will be told to try everything from vitamin B12 shots, to allergy medication, eat more kale and bananas. Perhaps if someone recently read a weston price website he will be advised to eat pork chops and drink buttermilk. Maybe polyphasic sleep is the answer? Or maybe light therapy and a white noise generator? At least this is Hacker News so nobody is recommending cupping or leeches or magnetic wristbands... yet. Asking the internet is like a schizophrenic consulting with the voices in his head. Every fruitcake idea will be presented with equal weight.
With that said, my contribution to the noise is that if these symptoms have been there for 18 years and haven't killed him, it's probably psychological.
By that logic, any chronic disease is psychological.
There are a lot of very smart people here and I think it was a great idea to come here. If the OP is smart enough to not take everything said as a cure, they could very well gain some very valuable bit of knowledge that could lead them on the right path; just like starting with Wikipedia.
In fact, if the diagnosis differs from what the computer says, then this should always be reported. Failure to do so should be considered a criminal offense.
Penalties are certainly a mistake in the case of your statement, as you haven't really outlined any computerized diagnostic system that is accurate on the entire range of human maladies, is available to all, and that can account for all of the fuzziness of reporting symptoms (just to name a few obstacles).
But I can't see at all where you're coming from when you say criminal offense. This would suggest that doctors should be locked up?
Then you feed it all the symptoms, sometimes it asks questions, and gives you a list of causes sorted by probability.
It works almost exactly like this game http://www.guessthename.com/
Apparently the biggest problem with it is that doctors won't use it.
The second problem is feeding data - you basically have to parse every medical paper ever published.
Here's a patent: http://www.freepatentsonline.com/6607482.html
There are lots of a papers, and a small number of working prototypes, but I have not heard of any that are actually being used.