Maltese cross appearance in peripheral blood smear is seen in which of the following infections?
**Core Concept**
The Maltese cross appearance in peripheral blood smear is a characteristic finding associated with the presence of red blood cell (RBC) agglutinins or cold agglutinins. This phenomenon occurs due to the binding of these antibodies to the surface of RBCs, leading to their aggregation and formation of a characteristic cross-like pattern.
**Why the Correct Answer is Right**
The correct answer is related to the presence of cold agglutinins, which are IgM antibodies that bind to the surface of RBCs at temperatures below 37°C. This binding causes the RBCs to clump together, forming a Maltese cross appearance on peripheral blood smear. The cold agglutinins are often seen in patients with infections such as Mycoplasma pneumoniae, which is a common cause of this phenomenon.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the Maltese cross appearance is not typically seen in infections caused by Staphylococcus aureus. While S. aureus can cause a range of infections, it is not commonly associated with cold agglutinins or the Maltese cross appearance.
**Option B:** This option is incorrect because the Maltese cross appearance is not typically seen in infections caused by Streptococcus pneumoniae. While S. pneumoniae can cause a range of infections, it is not commonly associated with cold agglutinins or the Maltese cross appearance.
**Option D:** This option is incorrect because the Maltese cross appearance is not typically seen in infections caused by Haemophilus influenzae. While H. influenzae can cause a range of infections, it is not commonly associated with cold agglutinins or the Maltese cross appearance.
**Clinical Pearl / High-Yield Fact**
It is essential to note that the Maltese cross appearance is a classic finding in the presence of cold agglutinins, which can be seen in patients with Mycoplasma pneumoniae infection. This can be a critical clue in the diagnosis of this infection, especially in patients with atypical presentations.
**Correct Answer: C. Mycoplasma pneumoniae**