QUIZ: No. 16, 03/05/2026

Diagnosis: Disseminated Fungal Infection

Findings: Multiple ill-defined hyperdense lesions involving bilateral cerebral hemispheres and cerebellum with surrounding edema. MRI demonstrates multiple bilateral lesions in the basal ganglia, cortical–subcortical regions, and posterior fossa, appearing T2/FLAIR hypointense centrally with surrounding hyperintense edema. Post-contrast images reveal irregular, crenated ring enhancement. There is no diffusion restriction on DWI and no blooming on SWI/GRE. MR spectroscopy shows reduced NAA, and abnormal clustered peaks in the 3.6–3.8 ppm region ( likely trehalose). Multiple bilateral centrilobular and peribronchial nodules with patchy areas of consolidation, predominantly in right lower lobe.

Discussion

Ø  Disseminated fungal infections, especially Aspergillus, occur in immunocompromised patients with impaired cell-mediated and innate immunity.

Ø  Primary infection begins in the lungs, followed by hematogenous dissemination to the brain and other organs. Aspergillus is angioinvasive, causing vascular invasion and tissue necrosis.

Ø  CNS involvement typically shows multiple lesions in basal ganglia, corticomedullary junction, and posterior fossa, often appearing T2 hypointense with irregular (crenated) ring enhancement.

Ø  Hyper density on CT in fungal lesions is due to accumulation of paramagnetic elements like iron and manganese within fungal hyphae.

Ø  Trehalose peak at 3.6–3.8 ppm on MRS is a characteristic marker of fungal infection. Trehalose is a disaccharide present in fungal cell walls.

Teaching pearl:

  T2 hypointense, irregular crenated ring-enhancing brain lesions without diffusion restriction strongly suggest fungal granulomas (aspergillosis).

  Presence of a peak in the 3.6–3.8 ppm region (trehalose) on MRS is a key clue favoring fungal infection .

P.S – BAL done in this case showed Aspergillus growth. CD4 count was 287 and NK cell was reduced. Patient is under evaluation to R/O Primary immunodeficieny disease (PID).