Haemoglobinuria does not occur in :
**Core Concept**
Haemoglobinuria is a condition characterized by the presence of haemoglobin in the urine, typically resulting from intravascular haemolysis. This condition can arise from various causes, including infections, autoimmune disorders, and enzymatic deficiencies.
**Why the Correct Answer is Right**
Haemoglobinuria occurs when haemoglobin is released into the bloodstream due to red blood cell destruction, and then filtered through the kidneys and excreted in the urine. In conditions where haemoglobin is not released into the bloodstream, such as intravascular haemolysis, haemoglobinuria will not occur. For instance, in cases of extravascular haemolysis, haemoglobin is removed from the circulation and broken down by macrophages in the spleen and liver, preventing its excretion in the urine.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because haemoglobinuria can occur in conditions like paroxysmal nocturnal haemoglobinuria (PNH), where there is intravascular haemolysis.
**Option B:** Incorrect because conditions like sickle cell disease, where there is chronic extravascular haemolysis, can lead to haemoglobinuria due to the breakdown of haemoglobin outside the bloodstream.
**Option C:** Incorrect because conditions like glucose-6-phosphate dehydrogenase (G6PD) deficiency, where there is extravascular haemolysis, can lead to haemoglobinuria due to the breakdown of haemoglobin outside the bloodstream.
**Clinical Pearl / High-Yield Fact**
Haemoglobinuria is often associated with conditions that lead to intravascular haemolysis, such as PNH, and can be a sign of underlying disease. When evaluating a patient with haemoglobinuria, it is essential to consider the underlying cause and investigate for conditions that may lead to this condition.
**Correct Answer: D**