Not Medical Advice: Yes. According to WebMD, in most cases, mono mildly affects the liver. In rare cases of mono, the liver fails.
Other major complications that can develop from mono include rupturing of the spleen, low blood platelet count, swelling of the lining of the brain or spinal cord, or inflammation of the brain itself. These complications are extremely rare.
Mononucleosis, often referred to as "mono," is a very common viral illness. About 90% of people over 35 have been infected with it, probably during early childhood, and have antibodies to the virus in their blood.
Check out some tips to prevent mononucleosis at Gustavus Adolphus College-Health Service.