Final answer:
Cytomegalovirus (CMV) infection is the disease that is usually self-limiting but requires ganciclovir for treatment in cases where medical intervention is necessary, particularly in immunocompromised patients.
Step-by-step explanation:
The disease that is usually self-limiting but is most commonly treated with ganciclovir if medical treatment is needed is Cytomegalovirus (CMV) infection. While most CMV infections are asymptomatic, it becomes important to treat this infection in immunocompromised patients such as those with AIDS, neonates, or transplant recipients due to the more severe effects it can have in such individuals. In comparison, while chickenpox and shingles, caused by the varicella-zoster virus, are typically treated with acyclovir, CMV is treated with ganciclovir due to its unique characteristics among herpesviruses.