A 22-year-old man comes to the urgent care clinic due to 2 weeks of fever, sore throat, and malaise. He has tried several over-the-counter products with minimal relief. The patient recently returned from a trip to Honduras for volunteer work. Temperature is 38.8 C (101.8 F), blood pressure is 130/70 mm Hg, pulse is 110/min, and respirations are 18/min. Mild jaundice is present. The tonsils are enlarged, erythematous, and covered with white exudates. Enlarged lymph nodes are palpable posterior to the sternocleidomastoid muscle bilaterally and in the axillary region. Breath sounds are normal. A grade 1/6 systolic murmur is heard in the left infraclavicular region. The abdomen is soft and nontender with normoactive bowel sounds; mild splenomegaly is present. Laboratory results are as follows: Which of the following is the most likely diagnosis in this patient?

Question

A 22-year-old man comes to the urgent care clinic due to 2 weeks of fever, sore throat, and malaise.  He has tried several over-the-counter products with minimal relief.  The patient recently returned from a trip to Honduras for volunteer work.  Temperature is 38.8 C (101.8 F), blood pressure is 130/70 mm Hg, pulse is 110/min, and respirations are 18/min.  Mild jaundice is present.  The tonsils are enlarged, erythematous, and covered with white exudates.  Enlarged lymph nodes are palpable posterior to the sternocleidomastoid muscle bilaterally and in the axillary region.  Breath sounds are normal.  A grade 1/6 systolic murmur is heard in the left infraclavicular region.  The abdomen is soft and nontender with normoactive bowel sounds; mild splenomegaly is present.  Laboratory results are as follows:  Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

11ec25c8_d458_5c1c_bc81_7980d76ced23_MD0003_00 Infectious mononucleosis, most commonly due to Epstein-Barr virus (EBV) infection, presents with prolonged fever, malaise, and sore throat. Physical findings include enlarged, erythematous tonsils with exudates; splenomegaly; and lymphadenopathy (commonly posterior cervical but may be generalized). Laboratory findings can include reactive leukocytosis, positive serum heterophile antibodies (Monospot test), and atypical lymphocytes on blood smear. Elevated transaminases are also seen in most patients due to mild, transient hepatitis. In addition, some patients develop autoimmune hemolytic anemia and thrombocytopenia, rare complications of infectious mononucleosis due to cross-reactivity of EBV-induced antibodies against red blood cells and platelets. In particular, IgM cold agglutinin antibodies cause complement-mediated destruction of red blood cells. This hemolysis, which can occur 2-3 weeks after the onset of EBV symptoms, may lead to jaundice, elevated bilirubin, and increased reticulocyte count, as seen in this patient. (Choice A) Acute hepatitis A infection can present with fever, malaise, jaundice, and hepatomegaly, particularly in patients who have recently traveled to developing countries. However, exudative tonsillitis, splenomegaly, and generalized lymphadenopathy are not typical features, and transaminase levels are usually much higher (often >1,000 U/L). (Choice B) Acute lymphoblastic leukemia can cause fever, malaise, hepatosplenomegaly, and generalized lymphadenopathy; however, bone marrow failure would cause a low, rather than an elevated, reticulocyte count, as in this patient. In addition, exudative pharyngitis does not occur. (Choice C) Bacterial endocarditis can present with prolonged fever, fatigue, and a cardiac murmur. However, this patient's soft systolic murmur is not typical of a pathologic murmur and is instead likely due to anemia (turbulent flow due to low blood viscosity). In addition, pharyngitis is not typically seen with endocarditis, and thrombocytopenia and liver function test abnormalities (including hyperbilirubinemia) are less likely. (Choice E) Plasmodium vivax causes malaria, which may present with fever, jaundice, hepatosplenomegaly, and anemia in a patient who has recently traveled to a tropical country. However, malaria causes cyclic fevers, and exudative pharyngitis and lymphadenopathy are not seen. Educational objective: Infectious mononucleosis typically presents with prolonged fever, malaise, exudative pharyngitis, splenomegaly, and generalized lymphadenopathy. Patients may develop autoimmune hemolytic anemia and thrombocytopenia up to 2-3 weeks after the onset of initial symptoms. References: Severe acute hepatitis and cold agglutinin-related hemolytic anemia secondary to prime infection with Epstein-Barr virus. (http://www.ncbi.nlm.nih.gov/pubmed/28376627) Infectious mononucleosis. (http://www.ncbi.nlm.nih.gov/pubmed/26424648)

A 22-Year-Old Man Comes to the Urgent Care Clinic Due