1. VARICELLA –ZOSTER VIRUS INFECTION
Varicella zoster virus causes two distinct clinical entities VARICELLA(CHICKEN POX) and HERPES ZOSTER(SHINGLES),the primary infection is chicken pox while the reactivation of latent varicella zoster is most common after sixth decade of life causes herpes zoster.VZV is demotropic and neurotropic.

2. shingles(herpes zoster)
It is reactivation of latent and dormant VZV in dorsal root ganglia that occurred later in life. Clinically burning discomfort appeared early in the affected dermatome then discrete vesicles unilaterally occurred 3-4 days later,cccasionally parasthesia occurs without rash (zoster sine herpete).
Severe disease ,widespread rash ,long duration of rash, and recurrence suggest underlying immunodeficiency.
Chickenpox can be contracted from zoster but not vice versa.

3. Dermatome involvement:
1-Thoracic dermatome is the most common one involved followed by 2-ophthalmic division of trigeminal nerve which might lead to corneal ulceration and need to urgent ophthalmology review because it lead to blindness.(zoster opthalmicus).
3-Ramsay hunt syndrome :it is facial palsy, ipsilateral loss of taste and buccal ulceration plus a rash in external auditory canal due to involvement of geniculate ganglion by VZV. THIS MAY BE MISTAKEN FOR BELL PALSY.4-sacral nerve involvement lead to bladder and bowel dysfunction.

4. Clinical manifestations:
The earliest feature of herpes zoster is severe pain before rash appeared (this enter in differential diagnosis of ischemic chest pain) this is followed in hours by an erythematous maculopapular rash evolve rapidly to vesicular lesions that is limited by unilateral dermatome characterestically the lesions in all stages of development are present.).the total duration of disease is 7-10 days however it may take as long as 2-4 weeks for the skin to returned to normal

5. complications 1-cranial nerve palsy 2- transverse myelitis
3-encephalitis
4-granulomatous cerebral angiitis
5-postherpetic neuralgia: it is the most common one causing troublesome persistence of pain for 1-6 months or longer following healing of rash, especially more common in advancing age.
6-pneumonitis
7-hepatitis
8-secondary bacterial infection.

6. 3- corticosteroid is controversial.
therapy
1-aciclovir(800 mg five times daily ) for 7-10 days. or related agent when commenced early has been shown to decrease both early and late onset pain, especially in patients over age 65 years.if the patient is immunocomromised the aciclvir should be given by IV route at dose of 10 mg per KG three times daily for 7 days.
2- aggressive analgesia for post herpetic neuralgia along with agents such as amitriptyline mg daily or gabapentin(commencing at 300 mg daily and increasing to 300 mg twice daily or more).
3- corticosteroid is controversial.

7. Clinical features of chicken pox
1-the incubation period is days.
2-The manifestation is more severe in adults ,immunocompromised and pregnant women.
3-the disease begun with vesicular eruption often on mucosal surface then disseminate on centripetal distribution (more dense on trunk and sparse on extremities)
4- new lesions occur every 2-4 days and with each crop fever is associated.

8. Clinical features of chicken pox
5-the rash progress from small pink macules to vesicles to pastules within 24 hours.(all stages of evolution appeared at the same time)
6-Infectivity last from 4 days before rash appear to last lesions crusted over.
7-adults,pregnant and immunocompromised at an increased incidence of visceral complications like pneumonitis. Hepatitis and encephalitis.

9. Complications of chickenpox:
1- pneumonitis :can be fatal especially in smoker.
2-hepatitis
3-encephalitis:rare
4-cerebellar ataxia:selflimiting and rare.
5-secondary bacterial infection from scratching is the most common.

10. Secondary bacterial infection is the most common and commonly by staph
Secondary bacterial infection is the most common and commonly by staph. While pneumonitis is the most serious developed more commonly in adults following chickenpox (20% of cases) that is why chicken pox is benign in children and more severe in adults. Also particularly more severe in pregnant women. Cerebral complications all are benign and self-limiting.

11. Diagnosis of chickenpox:
1-primarily clinical.
2-recognition of antigen by direct immunofluorescence to confirm diagnosis.
3-PCR for detection of DNA. FROM VESICULAR FLUID. To confirm the infection .
4-Serology is used to detect seronegative individuals at risk of infection.

12. management
1-Antiviral is needed for uncomplicated chickenpox when the patient presented within hours, otherwise treatment benefit is marginal and not indicated.
2-treatment is indicated in all patient with complications,immunocompromised and pregnant women regardless of duration of rash.