Dr. Karen Shackelford form BoardVitals joins us once again as we dig deep into a question about the hematopoietic and immune system.
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A 16-year-old male presents with a complaint of sore throat, fatigue and low-grade fever for three days. Exam reveals glossopharyngeal erythema with white exudates on his tonsils. He has enlarged posterior cervical lymph nodes and the posterior auricular lymph nodes are slightly enlarged. His spleen is palpable on abdominal exam. The throat culture is negative for strep and the monospot is positive. Which of the following findings are associated with the patient's diagnosis?
(A) Atypical lymphocyte
(B) Eosinophilia
(C) Howell-Jolly bodies
(D) Sickled erythrocytes
(E) Target cells
[Related episode: USMLE and COMLEX Prep: Glossopharyngeal Nerve Anatomy]
The correct answer here is A. The enlarged spleen could throw students off as it may make you think about Howell-Jolly bodies.
But this is a case of classical mononucleosis with fever, exudative pharyngitis, the tender lymphadenopathy, particularly posterior in the cervical and posterior auricular nodes. Adenopathy in the anterior nodes and the atypical lymphocytosis are the hallmarks of classic infectious mononucleosis.
The explanation to this question goes on to discuss the infection of the Epstein-Barr virus. It's a viral replication that begins in the oral pharyngeal epithelial cells with dissemination and infection of B-lymphocytes and the oropharyngeal lymphoid tissue.
There is more Step 1 detail here. The infected B-lymphocytes produce antibodies to the viral antigens. But they also produce another type of antibody which could be heterophile antibodies that are not antibodies to the virus, but antibodies to other tissues.
Active infection and the reinfection are regulated basically by the Epstein-Barr virus-specific T-lymphocyte. And atypical lymphocytes are activated. CDA plus T-cells and CD16 after killer cells appear in the blood at least 1-3 weeks after symptom onset.
Fatigue can persist forever – 6 months or longer in 13% of patients.
The splenic enlargement is a big caution for practitioners to remind their patients to avoid contact. The enlargement usually resolves after about 3 weeks. But even without contact, spontaneous splenic rupture is responsible throughout half of the cases. This usually occurs 2 weeks after symptom onset.
Eosinophilia is usually associated with parasitic infection.
The Howell-Jolly bodies were good distractor. They refer to the basophilic remnants of DNA. The circulating erythrocyte is usually removed in the spleen so they're found in patients who have either no spleen or 07:15.
Sickled erythrocytes are associated with sickle cell disease.
Target cells are associated with this disorder where the erythrocyte's cell surface is increased disproportionately to the cell volume. An example would be spherocytosis.