Match each clinical and neuroradiological presentation of central nervous system (CNS) dis… — USMLE Step 2 CK

Match each clinical and neuroradiological presentation of central nervous system (CNS) disease in a patient with advanced HIV to the most likely etiologic pathogen.

A $35$ -year-old patient with an absolute $\text{CD4}^+$ count of $80 \text{ cells/mm}^3$ presenting with fever, severe headache, and lethargy. Lumbar puncture reveals an opening pressure of $320 \text{ mm H}_2\text{O}$ , and MRI of the brain shows no focal parenchymal lesions.Cryptococcus neoformans
A $40$ -year-old patient with untreated HIV presenting with subacute onset of left-sided weakness and a generalized tonic-clonic seizure. MRI of the brain demonstrates multiple ring-enhancing lesions predominantly in the basal ganglia.Toxoplasma gondii
A $48$ -year-old patient with an absolute $\text{CD4}^+$ count of $35 \text{ cells/mm}^3$ developing progressive cognitive decline, ataxia, and visual field deficits. MRI of the brain reveals asymmetric, demyelinating white matter lesions without contrast enhancement or mass effect.JC virus
A $32$ -year-old patient with advanced AIDS presenting with rapidly progressive delirium and cranial nerve palsies. Fundoscopy shows retinal hemorrhages and exudates. MRI of the brain demonstrates prominent periventricular enhancement.Cytomegalovirus

Answer

Cryptococcus neoformans matches with high opening pressure and no focal lesions; Toxoplasma gondii matches with multiple ring-enhancing lesions; JC virus matches with non-enhancing white matter lesions; Cytomegalovirus matches with periventricular enhancement and retinitis.

Correct matching relies on recognizing the pathognomonic neuroimaging and clinical signs of HIV-associated CNS opportunistic infections. Toxoplasmosis typically causes ring-enhancing lesions; JC virus causes non-enhancing white matter disease; Cryptococcus causes a high opening pressure meningitis without large parenchymal lesions; and CMV causes periventricular enhancement with associated retinitis.

Step-by-Step Solution

Analyze the first presentation (elevated opening pressure without focal MRI lesions).

Identified as characteristic for Cryptococcal meningitis.

Cryptococcus typically invades the arachnoid granulations, blocking CSF resorption and causing high intracranial pressure without producing prominent parenchymal masses.

Analyze the second presentation (multiple ring-enhancing lesions in the basal ganglia).

Identified as characteristic for cerebral toxoplasmosis.

Toxoplasma gondii is the most common cause of mass lesions in advanced HIV, classically forming multiple inflammatory ring-enhancing abscesses.

Analyze the third presentation (asymmetric, non-enhancing white matter lesions).

Identified as characteristic for Progressive Multifocal Leukoencephalopathy (PML).

Reactivation of the JC virus causes demyelination of CNS white matter without a robust inflammatory response, resulting in a lack of contrast enhancement.

Analyze the fourth presentation (periventricular enhancement with retinal involvement).

Identified as characteristic for Cytomegalovirus (CMV).

CMV commonly affects the retina (retinitis) and can spread to the ependymal surfaces, causing periventricular inflammation and enhancement on neuroimaging.

Key Concept

Differentiation of central nervous system opportunistic infections in advanced HIV based on clinical and neuroimaging characteristics.

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