My brother has developed fever of unknown origin. what is it exactly?

Do definte diagnosis: We usually think of fevers as due to infection, but not all fevers are caused by infection. It can be causes by inflammatory diseases like rheumatoid arthritis, juvenile idiopathic arthritis, lupus, connective tissue diseases, tumors, familial mediterranean fever to name a fever. The diagnosis first depends on an indepth history and physical which takes time and then testing.

What it says: If the cause of a fever cannot be diagnosed in a few weeks, it is given the designation of fever of unknown origin. It may be due to exotic infections, malignancies, genetic defects, and autoimmune disorders etc. It often takes investigation by a team of specialists.