Mononucleosis is a disease that typically affects children and adolescents, but it can also develop in patients of other age groups. Symptoms of mononucleosis can be a cause for concern, such as an enlarged spleen and lymph nodes or night sweats. Mononucleosis may therefore be feared, but not rightly so: the disease usually resolves completely on its own and it is typical to contract it only once in a lifetime.