welcome redditors!to snoo-finity ... and beyond!

NBME 20 Answers

nbme20/Block 4/Question#7

A 33-year-old woman with HIV infection is brought ...

Non-Hodgkin lymphoma

Login to comment/vote.

 +6  upvote downvote
submitted by hayayah(525),

This is a primary central nervous system lymphoma. Most commonly associated with HIV/AIDS; pathogenesis involves EBV infection.

Considered an AIDS-defining illness. Variable presentation: confusion, memory loss, seizures. Mass lesion(s) (may be ring-enhancing in immunocompromised patient) on MRI, needs to be distinguished from toxoplasmosis via CSF analysis or other lab tests. Toxo usually has multiple ring enhancing lesions.

 +3  upvote downvote
submitted by radion(6),

Single enhancing lesion points more towards lymphoma than toxo. Toxo is usually multi-ring enhancing lesions.

 +2  upvote downvote
submitted by yotsubato(401),

It cant be Bacterial abscess (Nocardia) because shes taking TMP SMX.

It cant be toxo, because she has one lesion and is also taking TMP SMX which should improve her symptoms.

Glioblastoma is a disease of older individuals

Metastatic disease that mets to the brain is unlikely at this age.

CNS lymphoma is common in HIV AIDS patients, so that is the most likely choice.

mrglass  She's not taking TMP/SMX though. I would pick lymphoma over abscess mainly because .5cm growth in 2 weeks is incredibly rapid, which is classic for diffuse B-cell lymphoma, which is what tends to be in the CNS. Also there was no evidence of a classic source of brain abscess like mastoiditis. +