20. Disseminated disease
Most cases of herpes zoster follow the pattern described above, and they are limited to the reach of a given nerve. But some patients develop a disease that is not limited to dermatomes, and it is known as disseminated herpes zoster. It happens in 2% of cases of herpes zoster, but it is more common in immunocompromised patients. It is very difficult to differentiate from chickenpox or varicella. These patients develop more than ten vesicles outside the dermatome taken by the virus, and it develops one or two weeks after the classic manifestations of herpes zoster. In patients with disseminated disease, it is essential to rule out a cause of immunodeficiency, including HIV but also cancer and cancer treatment.