Infectious mononucleosis affects?
**Core Concept**
Infectious mononucleosis, also known as glandular fever, is a viral infection caused by the Epstein-Barr virus (EBV) that primarily affects the lymphoid tissues, particularly the lymph nodes, spleen, and liver.
**Why the Correct Answer is Right**
The correct answer is likely related to the hematologic manifestations of infectious mononucleosis. EBV infects B lymphocytes, which leads to their proliferation and activation. This results in the production of atypical lymphocytes, which can be seen in the peripheral blood smear. The infection also causes an increase in liver enzymes and can lead to splenomegaly due to the sequestration of lymphocytes and platelets in the spleen.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while the liver is involved in the disease, it is not the primary organ affected.
**Option B:** Incorrect because the question is likely asking for a specific organ or system affected, and the respiratory system is not the primary site of involvement.
**Option C:** Incorrect because while the lymph nodes are involved, the question is likely asking for a more specific organ or system affected.
**Clinical Pearl / High-Yield Fact**
A key clinical finding in infectious mononucleosis is the presence of atypical lymphocytes, which can be seen in 90% of patients. These cells are typically larger than normal lymphocytes, have a more irregular shape, and often have a distinctive "cowdry A" appearance.
**Correct Answer:** D.