Mononucleosis Epstein Barr Virus Infection

Mononucleosis is a common viral infection, particularly in adolescents and young adults, and has an incubation period of 30 to 45 days and a prodrome of 7 to 14 days.

Typically, mononucleosis is associated with an infection by the Epstein-Barr virus (EBV), which is a herpesvirus. Laboratory findings include leukocytosis, with more than half the leukocytes being lymphocytes. Approximately 10% to 15% of the mononuclear cells are atypical lymphocytes. Thrombocytopenia may develop with infectious mononu-cleosis. Almost 90% of patients with mononucleosis have abnormal liver enzymes. Mononucleosis is typically diagnosed by detecting a heterophile antibody, which is a nonspecific response to EBV infection. The heterophile antibody response is an IgM antibody that will agglutinate with the surface antigen of sheep and horse RBCs, but not with guinea pig kidney cells. Monospot tests are done with rapid slide agglutination procedures and horse RBCs to detect the heterophile antibody. Clinically, about 40% of patients have a positive heterophile antibody response at week 1, 60% at week 2, and 80% to 90% by week 3. The heterophile antibody usually persists for 3 to 6 months after an acute infection, less frequently up to 1 year. The heterophile antibody has an overall false-negative rate of 10% to 15%. However, in children under age 4 years, the heterophile antibody is falsely negative in 70% to 80% of cases. False-positive heterophile antibodies can occur with rubella, hepatitis, other viral infections, and lymphoma.

When the heterophile antibody is negative or the features of infectious mononucleosis are atypical, the disease can be confirmed with specific Epstein-Barr antibodies. Acute or recent infection is thought to be present if four serologic criteria are found: positive IgM to viral capsid antigen (VCA); high titers (>1:320) of IgG to VCA; positive early antigen antibody (anti-EA); and initial absence of antibody to Epstein-Barr nuclear antigens (EBNAs). The most useful EBV-specific antibody to diagnose acute mononucleosis is the IgM VCA, which appears soon after the onset of symptoms and has sensitivity of 91% to 98%

Table 15-18 Effects of Drugs on Lipid Values

Drug

Total Cholesterol

LDL Cholesterol

HDL Cholesterol

Triglycerides

Androgens

î

I

Antiepileptics

î

î

î

Thiazide diuretics

î/—

î

î

Beta blockers

I

î

Alpha blockers

î

1

Corticosteroids

î

î

î

î

Cyclosporine

î

î

C-19 Progestin

î

I

C-21 Progestin

I

Oral estrogens

1

1

î

î

Phenothiazines

î

I

î

Retinoids

î

î

I

î

Modified from Henkin Y, Como JA, Oberman A. Secondary dyslipidemia: inadvertent effects of drugs in clinical practice. JAMA 1992;267:961-968. HDL, High-density lipoprotein; LDL, low-density lipoprotein.

Table 15-19 Causes of Magnesium Abnormalities and specificity of 99%. Convalescent testing should document the appearance of IgG EBNA and disappearance of IgM VCA and anti-EA.

Syndromes mimicking infectious mononucleosis, but with negative heterophile antibodies, are considered heterophile-negative infectious mononucleosis. The most common syndromes are related to cytomegalovirus infection and toxo-plasmosis. Occasionally, viral hepatitis, rubella, lymphoma, leukemia, and the drugs isoniazid and phenytoin can cause a mononucleosis-like syndrome. Because heterophile antibodies are not uniformly positive early in the disease, serial tests may often be needed weekly to confirm mononucleosis. Specific serologic tests for EBV are relatively expensive and take longer to obtain results, so they are generally reserved for unclear cases and are not necessary in most patients with infectious mononucleosis. In an adolescent or young adult with appropriate clinical symptoms, heterophile antibodies are 95% sensitive and specific.

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