A 15-year-old boy is brought to the office due to fever. He has had fever, chills, fatigue, and myalgias for the past 10 days. He has lost some weight, which was attributed to poor appetite. Three weeks ago, the patient and his family returned from a trip to the Dominican Republic; he has not traveled anywhere else. There are no sick contacts at home. The patient has no significant medical history and takes no medications. Temperature is 38.3 C (101 F), blood pressure is 110/60 mm Hg, and pulse is 108/min. Physical examination shows a tired-looking boy in no acute distress. The tympanic membranes are not erythematous; mucous membranes are moist; and tonsils are enlarged and erythematous with white exudate. S1 and S2 are normal without murmurs. The lungs are clear to auscultation bilaterally. Lymphadenopathy is present in the anterior cervical, posterior cervical, axillary, and inguinal chains. The abdomen is soft and nontender. Laboratory results are as follows: The peripheral blood smear is shown in the image:
What is the most likely reason for these findings?

Question

A 15-year-old boy is brought to the office due to fever.  He has had fever, chills, fatigue, and myalgias for the past 10 days.  He has lost some weight, which was attributed to poor appetite.  Three weeks ago, the patient and his family returned from a trip to the Dominican Republic; he has not traveled anywhere else.  There are no sick contacts at home.  The patient has no significant medical history and takes no medications.  Temperature is 38.3 C (101 F), blood pressure is 110/60 mm Hg, and pulse is 108/min.  Physical examination shows a tired-looking boy in no acute distress.  The tympanic membranes are not erythematous; mucous membranes are moist; and tonsils are enlarged and erythematous with white exudate.  S1 and S2 are normal without murmurs.  The lungs are clear to auscultation bilaterally.  Lymphadenopathy is present in the anterior cervical, posterior cervical, axillary, and inguinal chains.  The abdomen is soft and nontender.  Laboratory results are as follows:  The peripheral blood smear is shown in the image:
 What is the most likely reason for these findings?

Quizplus · Accepted Answer

Explanation: This patient likely has infectious mononucleosis (IM), a disease most often due to the Epstein-Barr virus (EBV). IM is a systemic viral infection that is commonly seen in adolescents and young adults. Typical presenting signs and symptoms include fever, extreme fatigue, exudative pharyngitis or tonsillitis, lymphadenopathy (including posterior cervical nodes), and hepatosplenomegaly. Myalgias are common, and patients can develop anorexia (and resulting weight loss), nausea, or vomiting, possibly due to hepatocellular inflammation. The lymphocytes seen in this patient's peripheral smear, known as atypical reactive lymphocytes, are a further clue to the diagnosis. These cells, characterized by a predominant cytoplasm with an irregular nucleus, are commonly found with EBV infections; however, they are nonspecific and can also be seen in other systemic viral or inflammatory conditions. (Choices A and B) Although hematologic and lymphoproliferative malignancies (eg, acute lymphocytic leukemia, acute myeloid leukemia, Hodgkin disease) share some of the clinical features of IM (eg, fevers, lymphadenopathy, fatigue, weight loss), exudative pharyngitis is not a common feature. The smear would most likely demonstrate abnormalities such as blasts (with leukemia) or Reed-Sternberg cells (with Hodgkin disease). blasts Reed-Sternberg cells (Choice C) Parasitic infections may be seen in individuals who have traveled to endemic areas. Malaria can present with fever, fatigue, myalgias, and hepatosplenomegaly weeks after exposure to infection. However, it generally results in anemia and thrombocytopenia; classically causes cyclical fevers; does not typically cause exudative pharyngitis; and would be characterized by parasites (eg, ring forms) on the blood smear. ring forms (Choice D) Systemic bacterial infection would cause fever and fatigue. However, bacterial infections are typically associated with neutrophilic rather than lymphocytic predominance. In addition, symptoms of bacterial infection often accelerate rapidly in the absence of treatment; by day 10, the patient would have experienced sepsis and shock (eg, altered mental status, hypotension). Educational objective: Infectious mononucleosis, a systemic viral illness most frequently due to the Epstein-Barr virus, should be suspected in any adolescent with fever, fatigue, exudative pharyngitis or tonsillitis, lymphadenopathy, and hepatosplenomegaly. The presence of atypical lymphocytes in the peripheral smear can be a clue to its identification, although these cells may appear in other inflammatory conditions.

A 15-Year-Old Boy Is Brought to the Office Due to Fever