Chicken Pox and Shingles. This post will cover the points you need to know for your board exams as well as for teaching residents on the daily rounds. Please don't use the information here to treat your patients.
Both diseases are caused by the same Varicella-zoster virus (VZV) causing a vesicular eruption.
Chickenpox or Varicella is the primary airborne infection or by direct contact and is characterized by lesions on the face and trunk of various stages. The lesions are considered non-infectious after crusting.
Shingles or Herpes zoster is caused by a painful reactivation of the latent virus and involves a distribution of one or two adjacent dermatomes. It is mainly due to aging (loss of the VSV vaccine effect) and immunocompromised status (autoimmune diseases, transplant and HIV patients).
The most common complication of herpes zoster is postherpetic neuralgia (PHN) which is noticed to be less common in vaccinated people.
Aseptic meningitis can develop especially in immunocompromised patients and characterized by increased CSF proteins and VZV DNA, and CSF pleocytosis. Encephalitis may also occur and characterized by altered mental status. It may progress to leukoencephalitis that can be diagnosed with and MRI with a positive CSF PCR as well.
A sight-threatening complication is Herpes zoster ophthalmicus (HZO) which needs involves the ophthalmic division of the trigeminal nerve and extend to the eye in 50% of untreated patients.
Acute retinal necrosis (ARN) usually start in one eye and might spread to the other eye in up to 50% of cases.
Ramsay Hunt syndrome (herpes zoster oticus) is characterized by a triad of ipsilateral facial paralysis, ear pain, and vesicles visible in/out the ear.
Disseminated varicella can happen in immunocompromised patients and is characterized by DIC, vesicles, hemorrhagic lesions and pneumonia.
Diagnosis of VSV infections is usually clinical, no further testing usually needed. If the diagnosis is uncertain like in the case of hemorrhagic and disseminated disease, then you can do wound or CSF PCR testing (most sensitive) or direct fluorescent antibody (DFA) testing if PCR not available. Viral culture may be performed to guide antimicrobial therapy in resistant cases.
Treatment is highly recommended within the first 72 for all patients. If patient presents after that then it depends on the site involved and the overall clinical picture like age, new lesions developing and immunosuppression. If the lesions has completely crusted then no need for therapy. IV treatment is indicated in cancer patients with leukopenia or those with transplant history until clinical condition improves then the medication can be switched to PO. Treatment in general should continue until all lesions has crusted.
Medications include:
- Acyclovir 800 mg PO Q 4 hours (5 times daily)
- Acyclovir IV 10 mg/kg q 8hours
- Valacyclovir 1000 mg PO TID
- Famciclovir 500 mg PO TID
Acyclovir can be associated with crystal-induced acute renal failure. Check urine for birefringent needle-shaped acyclovir crystals.
Helpful book The Sanford Guide to Antimicrobial Therapy.
The information in this post is not for patients and shouldn't be used in treating patients. Please refer to your doctor for medical advice.