Immunocompromised hosts

Varicella in the immunocompromised host can be severe and life-threatening. Cell-mediated immunity appears to be the most important factor in the prognosis of primary varicella infection, as evidenced by the fact that patients who have pure humoral immune deficiency syndromes (such as Bruton agammaglobulinemia) do not seem to experience severe or protracted disease. As in immunocompetent individuals, administration of VZIG can prevent symptomatic infection, but it cannot clear an established infection.

Patients who have reticuloendothelial tumors and leukemia are at particularly high risk for severe disease. Risk is increased by concomitant administration of immunosuppressive therapeutic agents. Approximately 20% of patients who have leukemia develop “progressive varicella,” with fever to 40.5°C (105°F), continued cutaneous eruption for 7 to 10 days, deeper skin lesions, and diffuse involvement that includes palms and soles. Patients who have leukemia have difficulty clearing the viremia, and the virus disseminates to internal organs, most frequently the lung, but also the liver or central nervous system. Visceral dissemination occurs in from 7% to 32% of patients who have leukemia. VZV also causes substantial mor-bidity and mortality in bone marrow transplant recipients. One report of 140 patients documented zoster in 77, dissemination in 22, and death in 7.

The incubation period of VZV may be either shortened or prolonged in patients who are immunosuppressed and ranges from 8 to 24 days or even longer. The median is about 19 days. The incubation period is longer in those who receive VZIG.

Complications

Superinfection

The most common complication of primary varicella is bacterial superinfection of pox lesions. Cellulitis, impetigo, or adenitis can be seen. These infections usually are caused by staphylococcal or streptococcal species and sometimes are mixed. In recent years, an increasing number of reports have linked group A beta-hemolytic streptococcal infection with varicella. Group A streptococci can cause a rapidly progressive cellulitis or necrotizing fasciitis. For this reason, patients who develop cellulitic infection during the course of primary varicella should be observed carefully for progression and treated aggressively if rapid progression occurs. Often, surgical debridement and skin grafting are required. Hyponatremia and/or hypocalcemia suggest ongoing necrotizing fasciitis. Group A streptococcal pneumonia also has been associated with primary varicella; it tends to produce medium-to-large pulmonary effusions, and its course is marked by prolonged fever and slow recovery, even with appropriate antimicrobial therapy.

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