Share Medical Knowledge: Herpes Zoster

Wednesday, February 17, 2010

Herpes Zoster

5:04 AM |

Diposkan oleh Hermanto | Edit Post

Definition

Herpes zoster is the recidivans form of varicella-zoster virus infection. The primary infection varicella or chickenpox most commonly occurs as an acute childhood exanthem.

The virus establishes latent infection in sensory ganglia at the base of the brain and spinal column. As the cell-mediated immune response conferred at the time of primary infection wanes, the disease increases in incidence. Certain provoking factors and concomitant illness are associated with attacks.

Onset

Zoster attacks may occur in children and young adults, but are quite rare.
Severe or prolonged attacks, especially in young persons, should raise concern about concomitant illness and immune status.

Provoking Factors

Immunosuppression, whether iatrogenic or secondary to disease.
Hemorrhagic zoster lesions or zoster of unusual severity in a young host should raise suspicion of underlying disease such as lymphoma, hematologic malignancies, or HIV disease.
Physical trauma to infected sensory ganglia, and occasionally to peripheral nerves, can trigger attacks.
Radiation therapy of solid tumors and spinal manipulation are among the other common causes.

Clinical Manifestation

Most cases of herpes zoster present with pain that is variously described as shock-like or a continuous burning sensation with hyperalgesia. Other patients experience less intense but equally uncomfortable crawling or pruritic parasthesias, and find that even fabric touching the area is intolerable.
Within 2 or 3 days, and rarely as long as a week, skin lesions develop within the anatomic area of the involved nerve segment. These lesions, like those of herpes simplex virus (HSV), consist of tightly grouped vesicles on an erythematous, urticarial base. The lesions are usually more extensive than those of HSV and may be continuous or, more often, exhibit skip areas within the neurologic segment.
Mild constitutional symptoms of fatigue and lassitude may precede the skin lesions, but fever is rare.
Uncomplicated zoster in children usually is mild and often painless. It can run its entire course in 2 weeks or less, and normally clears without sequelae. In young adults, the average course is 2 to 3 weeks long, pain is mild to moderate, and sequelae are rare.

The following anatomic locations are most frequently involved:

· Thoracic dermatomes 53%

· Cervical dermatomes 20%

· Trigeminal nerve 15%

· Lumbosacral dermatomes 11%

Dermatologic Physical Exam

Primary Lesions

1. Erythematous urticarial plaque or plaques within a dermatome segment or contiguous dermatomes.

2. Grouped 3- to 5-mm vesicles that evolve and often umbilicate.

3. Pustules that replace vesicles as the lesions mature.

Secondary Lesions

1. Erosions as blisters and pustules rupture.

2. Crusting as pustules dry and shrink or due to secondary infection.

3. Hemorrhage into vesicles.

4. Necrosis and gangrene in severe lesions having an active vascular component.

5. Postinflammatory hyperpigmentation, common even in uncomplicated zoster.

6. Scarring, more common in older patients or in zoster that is associated with underlying systemic disease.

Distribution

Microdistribution: None.

Macrodistribution: Follows a dermatome segment or contiguous neural segments.

Laboraotry studies

Tzanck Smear

· A smear of material from a fresh ruptured blister base is placed on a glass slide and immediately stained with Giemsa or some similar stain.

· A positive smear will show herpesvirus effect by the presence of keratinocytes with balloon nuclei and multinucleated giant cells with similar changes.

· This test is rapid and inexpensive, and can be performed with equipment that is readily accessible.

· Sensitivity, in experienced hands, from a fresh vesicle approaches or exceeds 70%.

Biopsy

· Biopsy of a zoster lesion shows pathognomonic features, but is usually done only to investigate a lesion that is clinically atypical.

· Biopsy does not distinguish HZV from HSV- 1 or HSV-2, and adds nothing if the lesions are clinically diagnostic.

Complement Fixation Tests

· These titers rise rapidly following onset, and are useful in atypical infections.

Viral Culture

· Although culture is very specific and will distinguish HZV from HSV-1 and HSV-2, sensitivity is low (50% or less).

· Cultures may be used to confirm the diagnosis in unusual cases. In otherwise clinically typical cases, culture is unnecessary and the diagnosis can usually be confirmed by Tzanck smear or RIF test.

Rapid Immunofluorescence Test (RIF) for Herpes

· This test employs a monoclonal antibody system and exhibits a sensitivity of about 65%.

· In addition to speed, RIF can distinguish among HZV, HSV-1, and HSV-2.

· The specimen consists of a smear from a blister, and the test is practical and reproducible. Results are available in 1 hour or less after receiving the specimen.

Polymerase Chain Reaction (PCR)

· PCR testing performed from blister specimens shows a sensitivity of 97%, which is superior to culture.

· PCR is rapid and can distinguish HZV from HSV-1 and HSV-2.

· It is positive when performed from crusts and material from involuting lesions where culture, Tzanck, and RIF results are less reliable.

· The technology is expensive and not universally available at present.

Complications

Generalized zoster

In addition to the problems associated with the special forms reviewed above, one of the most serious complications is generalized herpes zoster. Many patients will develop a few scattered lesions that are out of the primary neurologic segment. When extensive lesions occur along with fever and systemic toxicity, however, it is an indication of general viremia.

Postherpetic neuralgia (PHN)

It is the most common complication of herpes zoster. The incidence peaks in patients in their sixth and seventh decades, probably due to more severe attacks and lowered capacity to regenerate after nerve injury.

Pain or altered nerve function persisting more than 30 days after the onset of skin lesions is considered PHN. Of those with persisting pain or altered sensation, a large number gradually improve and clear over several months. Lancinating pain, hyperalgesia, and crawling dysesthesias are most common.

Other rare complications: