Blood and Lymphoreticular System 1 out of 292
A 7-year-old boy is brought to the physician by his father because of a 1-day history of a pruritic rash on his trunk and face. Five days ago, he developed low-grade fever, nausea, and diarrhea. Physical examination shows a lace-like erythematous rash on the trunk and face with circumoral pallor. The agent most likely causing symptoms in this patient has selective tropism for which of the following cells?
Erythroid progenitor cellsA 7-year-old patient with a pruritic, lace-like erythematous rash on his trunk and face that developed 5 days after a low-grade fever, nausea, and diarrhea most likely has a parvovirus B19 infection. Parvovirus B19 has selective tropism for erythroid progenitor cells. Infection of these cells can result in temporary suspension of erythropoiesis, which leads to transient aplastic crisis. Sensory neuronal cellsCertain pathogens (e.g., VZV, HSV-1, or HSV-2) display tropism for sensory neuronal cells and remain dormant within sensory nerve ganglia following primary infection. A primary infection with VZV typically manifests with a pruritic rash and fever, which are seen in this patient. However, the rash would be more widespread, involving not only the face and trunk, but also the scalp, extremities, oral and urogenital mucosa, palms, and soles. Herpes simplex virus infections typically only cause localized symptoms (aphthous stomatitis, herpes labialis, or herpes genitalis). Epithelial cellsCertain pathogens (e.g., group A β‑hemolytic streptococci) display tropism for epithelial cells. Infection with GAS can cause scarlet fever, which manifests with an erythematous rash, perioral pallor, and fever, which are seen in this patient, but it would typically also cause pharyngitis and a white or strawberry tongue. T lymphocytesCertain pathogens (e.g., VZV and HIV) display tropism for T lymphocytes. Given this patient's age, he could have chickenpox caused by a primary infection with VZV. Chickenpox typically manifests with a pruritic rash and fever, which are seen here. However, the rash would be more widespread, involving not only the face and trunk, but also the scalp, extremities, oral and urogenital mucosa, palms, and soles. Moreover, a characteristic feature of chickenpox is the simultaneous occurrence of various stages of rash (macules, papules, vesicles, crusted papules), which is not seen in this patient. B lymphocytesCertain pathogens (e.g., EBV) display tropism for B lymphocytes. Infection with EBV can cause infectious mononucleosis, a highly contagious condition, which spreads via saliva (hence the name “kissing disease”). EBV infection can manifest with fever and pruritic rash, which are seen in this patient, but acute pharyngitis, tonsillitis, lymphadenopathy, and splenomegaly would also be expected. MonocytesCertain pathogens (e.g., the measles virus and CMV) display tropism for monocytes. While measles typically manifests with conjunctivitis, coryza, and cough, followed by sudden development of a high fever, malaise, and an erythematous, maculopapular rash, this patient presents with low-grade fever and a lace-like erythematous rash with perioral sparing. CMV infection usually remains asymptomatic in immunocompetent patients.
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