A 35-year-old HIV-positive female on irregular ART presents with headache, confusion, fever, and right-sided weakness. Her CD4 count is 40 cells/mm³. MRI brain shows multiple ring-enhancing lesions in the basal ganglia. What is the most likely diagnosis?

1. A

   A. Cerebral toxoplasmosis

2. B

   B. Primary CNS lymphoma

3. C

   C. Progressive multifocal leukoencephalopathy (PML)

4. D

   D. Neurocysticercosis

Appeared in: INI-CET EXAM -2026

Explanation

• Cerebral toxoplasmosis is the most common cause of focal, space-occupying brain lesions in patients with AIDS.
• The patient's extremely low CD4 count of 40 cells/mm3 places her at high risk for this specific opportunistic infection, which typically occurs when CD4 counts are below 100 cells/mm3.
• The clinical triad of fever, headache, and focal neurological deficits (right-sided weakness) is highly characteristic.
• The MRI finding of multiple ring-enhancing lesions, particularly in the basal ganglia, is the classic radiological presentation of cerebral toxoplasmosis.

Why Other Options Were Wrong

• Option B: Primary CNS lymphoma is the second most common cause and a key differential. However, it is statistically less common than toxoplasmosis and often presents as a single, larger, periventricular lesion, although multiple lesions can occur.
• Option C: Progressive multifocal leukoencephalopathy (PML) is caused by the JC virus and characteristically presents with non-enhancing white matter lesions on MRI. The presence of ring enhancement and mass effect makes PML unlikely.
• Option D: Neurocysticercosis is caused by the larvae of the tapeworm Taenia solium. While it can cause ring-enhancing lesions, it is not as strongly associated with severe HIV-related immunosuppression as toxoplasmosis and is more common in endemic regions. A pathognomonic finding is a scolex within the cyst, which was not mentioned.

Related Visual

Clinical Relevance

• Nursing practice connection: Use the key finding related to Diagnosis of CNS opportunistic infections in HIV/AIDS patients to guide bedside assessment, documentation, and the next nursing action.
• In a patient with AIDS and suspected cerebral toxoplasmosis, prompt initiation of empirical therapy (e.g., pyrimethamine, sulfadiazine, and leucovorin) is a standard practice and can be both diagnostic and therapeutic.
• Nurses play a vital role in monitoring the patient's neurological status, administering medications, managing symptoms like seizures and fever, and educating the patient about the importance of adherence to both ART and opportunistic infection treatment.
• What if? If the patient's MRI had shown a single, large, solid-enhancing lesion crossing the corpus callosum, the primary suspicion would shift from toxoplasmosis to Primary CNS Lymphoma, and a brain biopsy would be more urgently considered.

How to Approach the Question

• First, identify the key patient demographic: a 35-year-old female with HIV and a very low CD4 count (40), indicating severe immunosuppression (AIDS).
• Next, correlate the clinical presentation: a subacute onset of headache, fever, confusion, and a focal neurological deficit (right-sided weakness).
• Then, focus on the most specific diagnostic clue provided: the MRI finding of 'multiple ring-enhancing lesions in the basal ganglia'.
• Synthesize these three pieces of information. The combination of severe immunosuppression and multiple ring-enhancing brain lesions is a classic pattern.
• Evaluate the options by recalling the typical presentations of CNS opportunistic infections in AIDS. Cerebral toxoplasmosis is the most common cause fitting this exact clinical and radiological picture.

Concept Tested & Keywords

• Concept Tested: Diagnosis of CNS opportunistic infections in HIV/AIDS patients.
• Stem keywords: HIV-positive, irregular ART, headache, confusion, fever, right-sided weakness, CD4 count 40, MRI
• Lead-in keywords: most likely diagnosis
• Clinical cues: CD4 count of 40 cells/mm3 indicates severe immunosuppression (AIDS).
• Clinical cues: Multiple ring-enhancing lesions on MRI is a classic radiological sign.

Question ID

QBxbmGokCSAPAP6D608wn6

Copy ID

Reference Book

E6 Medicine Davidson Principles Practice 24e p. 340-342

E6 Robert Boland, Marcia L. Verduin - Kaplan and Sadock's Comprehensive Text of Psychiatry-Wolters Kluwer Health (2024) (pp 1-16525 of 16525) pp. 2005-2007, 2004-2006