Cause of methaemoglobinemia are all except :
**Core Concept**
Methaemoglobinemia is a condition characterized by an abnormal amount of methaemoglobin, a form of haemoglobin, in the blood. This condition can be caused by various factors, including certain medications, chemicals, and medical conditions. **Methaemoglobin** has a lower affinity for oxygen, leading to tissue hypoxia.
**Why the Correct Answer is Right**
The correct answer is not provided, however, common causes of methaemoglobinemia include certain medications like **prilocaine**, **nitroglycerin**, and **dapsone**, as well as chemicals like **aniline** and **nitrites**. These substances can induce the formation of methaemoglobin by oxidizing haemoglobin.
**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific option, it's challenging to provide a detailed explanation. However, if an option listed a known cause of methaemoglobinemia, it would be incorrect as the answer because the question asks for exceptions.
**Option B:** Similarly, without the specific text, we can't determine why it's incorrect, but if it's a recognized cause, it doesn't fit the question's criteria.
**Option C:** Again, lacking the specific option, we can only speculate that if it's a known inducer of methaemoglobinemia, it would not be the correct answer.
**Option D:** This option, if it represents a substance or condition not associated with methaemoglobinemia, could potentially be the correct answer based on the question's phrasing.
**Clinical Pearl / High-Yield Fact**
Methaemoglobinemia is a critical condition that can lead to significant morbidity and mortality if not recognized and treated promptly. A key clinical feature is **cyanosis** that does not respond to oxygen therapy, highlighting the importance of early diagnosis.
**Correct Answer:** Correct Answer: D. Nitric oxide