A 19-year-old male presents with a 1-week history of malaise and anorexia followed by fever and sore throat....

A 19-year-old male presents with a 1-week history of malaise and anorexia followed by fever and sore throat.
On physical examination, the throat is inflamed without exudate. There are a few palatal petechiae. Cervical adenopathy is present. The liver is percussed at 12 cm and the spleen is
palpable. Throat culture: negative for group A streptococci
Hct: 38%, Hgb: 12 g/dL, Reticulocytes: 4%
WBC: 14,000/μL, Segmented: 30%, Lymphocytes: 60%, Monocytes: 10%
Bilirubin total: 2.0 mg/dL (normal 0.2 to 1.2)
Lactic dehydrogenase (LDH) serum: 260 IU/L (normal 20 to 220)
Aspartate (AST): 40 U/L (normal 8 to 20 U/L)
Alanine (ALT): 35 U/L (normal 8 to 20 U/L)
Alkaline phosphatase: 40 IU/L (normal 35 to 125)

The most important initial test is
a. Liver biopsy
b. Strep screen
c. Peripheral blood smear
d. Toxoplasmosis IgG
e. Lymph node biopsy

Answer: c. Peripheral blood smear

The most important serum test is
a. Heterophile antibody
b. Hepatitis B IgM
c. Cytomegalovirus IgG
d. ASLO titer
e. Hepatitis C antibody

Answer: a. Heterophile antibody

Corticosteroids would be indicated if
a. Liver function tests worsen
b. Fatigue lasts more than 1 week
c. Severe hemolytic anemia is demonstrated
d. Hepatitis B is confirmed

Answer: c. Severe hemolytic anemia is demonstrated

Discussion:

This young man presents with classic signs and symptoms of infectious mononucleosis. In a young patient with fever, pharyngitis, lymphadenopathy, and lymphocytosis, the peripheral blood smear should be evaluated for atypical lymphocytes. A heterophile antibody test should be performed.
The symptoms described in association with atypical lymphocytes and a positive heterophile test are virtually always due to Epstein-Barr virus.

Neither liver biopsy nor lymph node biopsy is necessary. Workup for toxoplasmosis
or cytomegalovirus infection or hepatitis B and C would be considered in heterophile-negative patients, Hepatitis does not occur in the setting of rheumatic fever, and an antistreptolysin O titer is not indicated.

Corticosteroids are indicated in the treatment of infectious mononucleosis when severe hemolytic anemia is demonstrated or when airway obstruction occurs. Neither fatigue nor the complication of hepatitis is an indication for corticosteroid therapy.