Q&A Medicine>>>>>Neurology
Question 4#

A 43-year-old HIV positive man presents with new onset right-sided paralysis. He recently started trimethoprim–sulfamethoxazole (TMP– SMX) for a CD4 count of 70/mm3 . The patient is afebrile and vital signs are within normal limits. Neurologic examination demonstrates hyper-reflexia, hypertonia, and positive Babinski sign on the right side.

Which of the following is the most likely diagnosis in this patient?

a. Progressive multifocal leukoencephalopathy (PML)
b. Primary CNS lymphoma
c. AIDS dementia complex
d. Toxoplasmosis

Correct Answer is A


Progressive multifocal leukoencephalopathy (PML). The patient in this question is likely suffering from PML, an opportunistic infection seen in immunocompromised patients that is caused by the JC virus (a human polyomavirus that has an unknown mode of transmission). This disease typically involves cortical white matter and does not produce a mass effect. Symptoms typically include hemiparesis, speech disturbances, and vision and gait changes. CT scan shows several nonenhancing cerebral demyelinating white matter lesions without any mass effect. There is no treatment for PML and the prognosis is poor. (B) Primary CNS lymphoma is the second most common cause of mass lesions (following toxoplasmosis) in HIV-infected patients. This involves a ring-enhancing lesion that is solitary and typically periventricular. The diagnosis is confirmed by EBV DNA in the cerebrospinal fluid (CSF). (C) AIDS dementia complex will demonstrate cortical atrophy and ventricular enlargement. (D) Toxoplasmosis is the most common ringenhancing mass lesion in HIV-infected patients. Lesions are multiple, spherical, and typically located in the basal ganglia. This is unlikely given that the patient is currently taking TMP–SMX.