A 19-year-old man comes to the office with a 2-week history of fever, fatigue, and sore throat. He has no diarrhea or rash. The patient has no significant medical history. He occasionally uses tobacco and alcohol; he has smoked marijuana several times but has never used injectable drugs. The patient is sexually active with one partner and uses condoms occasionally. Temperature is 39 C (102.2 F), blood pressure is 110/70 mm Hg, pulse is 88/min, and respirations are 16/min. Physical examination shows enlarged tonsils with white exudates. Enlarged, tender, mobile nodes are palpable along the cervical, axillary, and inguinal chains bilaterally. The examination is otherwise unremarkable. Which of the following tests is most likely to yield the diagnosis in this patient?
Infectious mononucleosis | |
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This patient's symptoms are suspicious for infectious mononucleosis (IM), which is typically caused by Epstein-Barr virus (EBV). IM is classically characterized by a prolonged course (up to 1 month) of fever, exudative pharyngitis, and tender lymphadenopathy; the adenopathy is commonly located in the posterior cervical region but may be generalized, as in this case. Fatigue is common and may persist for months, beyond the resolution of other symptoms. In addition, splenomegaly occurs in the majority of patients, and splenic rupture is a rare but dangerous complication.
Diagnosis is with the heterophile antibody (Monospot) test, which is a specific test that detects EBV antibodies that agglutinate to horse red blood cells. Heterophile antibodies arise within a week of symptoms (25% false-negative rate during the first week of illness) and persist for up to a year. The heterophile antibody test is not accurate in children age <4, for whom serum anti-EBV antibody testing is recommended instead.
(Choice A) Cytomegalovirus (CMV) causes a constellation of symptoms similar to IM. However, IM caused by EBV is much more common, and pharyngitis is less commonly seen in CMV.
(Choice C) Acute HIV infection also causes fever, malaise, and generalized lymphadenopathy, and testing should be performed in this patient. However, adenopathy in acute HIV is nontender and tonsillar exudates are uncommon. In addition, rash and diarrhea are present in most patients with acute HIV. Therefore, IM is a more likely diagnosis.
(Choice D) Lymph node biopsy is indicated when there is high suspicion for malignancy, such as a patient with fever, weight loss, and nontender lymphadenopathy. Tender, mobile nodes are more suggestive of infection than malignancy.
(Choice E) Neisseria gonorrhoeae is a sexually transmitted infection that can present as an extragenital infection (eg, conjunctivitis, pharyngitis, arthritis). Isolated gonococcal pharyngitis is not typically associated with systemic symptoms (eg, fever, generalized lymphadenopathy, malaise) as seen in this patient.
(Choice F) A rapid streptococcal antigen test is positive in streptococcal pharyngitis, which can cause fever, pharyngitis, and tender cervical lymphadenopathy. However, streptococcal pharyngitis is unlikely to cause generalized lymphadenopathy, and symptoms typically resolve within a week even without treatment. This patient's prolonged symptoms are more likely due to EBV.
Educational objective:
Infectious mononucleosis causes prolonged fever, pharyngitis, fatigue, and lymphadenopathy and is diagnosed by the heterophile antibody (Monospot) test.