Coxsackievirus can cause hand, foot, and mouth disease as well as herpes pharyngitis. Herpes pharyngitis and HFMD are usually self-limiting diseases that resolve and completely heal within a week or so. In a few cases, there are complications, and children with complications may have residual effects. Coxsackievirus is not self-resolving if not treated well, so it should also be taken seriously. Hand, foot, and mouth disease and herpes pharyngitis caused by coxsackieviruses have possible complications such as myocarditis, inflammation of the liver, meningoencephalitis, and even brainstem encephalitis. The most serious is brainstem encephalitis, which can lead to severe hand, foot and mouth disease or herpes pharyngitis, which is likely to be life-threatening and must be taken seriously.