Diagnosis of mononucleosis follows the exhibition of a large number of abnormal white blood cells (lymphocytes) on microscopic blood examination. These blood cells have a single nucleus that give the disease its name. Symptoms are varied but include enlarged lymph nodes, sore throat, fever, enlarged spleen in about half the cases, and excessive fatigue. Occasional rashes and throat and mouth infections occur. Liver inflammation is common. Fatalities are very rare and, when they do occur, usually result from splenic rupture. General therapeutic measures include bed rest and treatment of symptoms.