While there are many learning disorders that involve the inability to read or spell different words there are very few that are as specific to learning one specific field of study the way Dyscalculia is. Dyscalculia as you may have gotten an inkling from the name, deals with difficulty in studying mathematics specifically. Dyscalculia is basically the Dyslexia of the arithmetic genre.
Much like Dyslexia, which can make sufferers read one word as the exact opposite or even not be able to see certain letters, Dyscalculia usually manifests itself the most often by having sufferers struggle with being able to tell the difference between one symbol or another. This means that when a problem like five plus five is on a piece of paper, the sufferer of Dyscalculia will see the problem as five minus five or even five times five. Of course the answer to the equation is drastically different if the symbol that helps solve the problem shows up as anything other than what it actually is. Also like Dyslexia, because mathematics can be very difficult for quite a few students anyway, it can be extremely hard to see exactly where the problem is lying when it comes to solving the equation.
Perhaps the worst news in regards to Dyscalculia is that doctors and scientists are still pretty stumped as to what causes the disorder and what sort of treatments work the best to counter the effect. This means that really the only way people have been able to overcome the disorder is to constantly work the problem and have come to accept that to some degree they simply are not going to be able to match their peers when it comes to math scores and accomplishments. Unlike Dyslexia, which does have a set prescribed treatment that can make it less effectual, Dyscalculia remains with the person and can negatively affect them for the remainder of their life.