FDG PET/CT Enables More Precise Identification of Multiorgan Involvement in Brazilian Paracoccidioidomycosis

A study conducted by researchers at the Brazilian CEPID CancerThera center shows that molecular imaging with fluorodeoxyglucose (FDG) PET/CT can detect systemic lesions of paracoccidioidomycosis (PCM) more sensitively than conventional staging methods, helping to reassess the extent and severity of the disease. The findings were published in Clinical Infectious Diseases.

Paracoccidioidomycosis is a systemic fungal disease caused by inhalation of fungal spores of the Paracoccidioides genus, with significant clinical and epidemiological importance in Brazil. Often referred to as “coffee planter's disease,” it primarily affects the lungs but can also spread to multiple organs via lymphatic and hematogenous routes. Conventional staging typically relies on physical examination, serological tests, and chest X-rays, which may underestimate extrapulmonary involvement and inflammatory burden.

The research team prospectively evaluated 34 patients with confirmed paracoccidioidomycosis, including untreated patients and those with suspected treatment failure. All patients underwent conventional clinical staging and whole-body FDG PET/CT. Results showed that PET/CT identified 150 lesions, compared to 62 detected by conventional assessment—more than double the number. PET/CT also revealed new lesion sites not diagnosed by conventional workup, particularly in lymph nodes, lungs, and adrenal glands.

The study showed that PET/CT reclassified 97% of cases as multifocal disease and increased the proportion of severe cases from 70.6% to 91.2%. The researchers believe this demonstrates that FDG PET/CT provides greater accuracy in assessing disease extent and severity, and may also influence treatment planning and determination of treatment duration.

FDG is a glucose analog radiotracer that produces imaging signals in areas of active energy metabolism. Infectious and inflammatory lesions are typically metabolically active and therefore appear more clearly on PET/CT images. The study also analyzed metabolic quantitative parameters including SUVmax, total metabolic lesion volume (TMLV), and total lesion glycolysis (TLG). Results showed that these parameters correlated significantly with traditional inflammatory markers such as serological titers, C-reactive protein, and erythrocyte sedimentation rate.

The researchers also compared FDG PET/CT with gallium-67 scintigraphy. Results showed that PET/CT detected approximately four times more sites of active infection than gallium-67 scintigraphy, while providing images with higher anatomical resolution in a shorter acquisition time.

The research team stated that the next step is to further validate these findings through multicenter studies with larger sample sizes, and to clarify in which clinical scenarios PET/CT provides the greatest benefit, including disease staging, determination of treatment duration, and monitoring of specific organ involvement.