24 Year old AIDS patient develops chronic abdominal pain, low grade fever, diarrhoea, malabsorption. Oocysts demonstrated in stool. Likely cause of his diarrhoea is –
**Core Concept**
The underlying condition being tested involves a opportunistic infection in an immunocompromised patient, specifically one with AIDS. This patient's symptoms of chronic abdominal pain, low-grade fever, diarrhea, and malabsorption, along with the demonstration of oocysts in the stool, point towards an intestinal parasitic infection.
**Why the Correct Answer is Right**
The correct answer is related to an organism that is a common cause of diarrhea in AIDS patients, characterized by the presence of oocysts in the stool. This organism is typically *Cryptosporidium*, which causes cryptosporidiosis. The infection leads to severe, chronic diarrhea and malabsorption in immunocompromised individuals.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while other pathogens can cause similar symptoms, they are less commonly associated with oocysts in stool.
**Option B:** Incorrect as it does not match the description of the pathogen causing the patient's symptoms.
**Option C:** Incorrect because it is not the primary cause of the described symptoms in an AIDS patient.
**Clinical Pearl / High-Yield Fact**
In AIDS patients, opportunistic infections such as cryptosporidiosis are critical to recognize due to their impact on the patient's quality of life and potential for severe complications. The presence of oocysts in the stool is a key diagnostic feature.
**Correct Answer:** D. Cryptosporidium.