Multiple-Organ Involvement in Familial Hemophagocytic Lymphohistiocytosis Type 2 Shown on FDG PET/CT

Emerging Trends in Radionuclide Imaging of Infection and Inflammation in Pediatrics: Focus on FDG PET/CT and Immune Reactivity

The most common indication for ¹⁸F-FDG PET/CT is tumor imaging, which may be performed for initial diagnosis, staging, therapeutic response monitoring, surveillance, or suspected recurrence. In the routine practice of pediatric nuclear medicine, most infectious, inflammatory, and autoimmune processes that are detected on ¹⁸F-FDG PET/CT imaging - except for imaging in fever or inflammation of unknown origin - are coincidental and not the main indication for image acquisition. However, interpreting these "coincidental" findings is of utmost importance to avoid erroneously attributing these findings to a neoplastic process. We review the recent literature on fever of unknown origin as well as inflammation of unknown origin in pediatrics and then focus on the ¹⁸F FDG PET/CT imaging findings seen in two specific entities with increased immune reactivity: hemophagocytic lymphohistiocytosis syndrome and the immune-related adverse events associated with checkpoint inhibitors. We will subsequently close with two sections highlighting related topics and relevant references for further reading.

Simultaneous Detection of 2 Types of Malignancies in a Pediatric Patient on FDG PET/CT Led to Diagnosis of Li-Fraumeni Syndrome

ABSTRACT

A 17-month-old girl underwent FDG PET/CT to evaluate a right adrenal lesion, which showed abnormal 18 F-FDG avidity. In addition, an unexpected lesion with mild 18 F-FDG uptake was noted in the right anterior thoracic wall. Pathology demonstrated adrenocortical carcinoma in the right adrenal and rhabdosarcoma in both the left forearm and right anterior thoracic wall. Gene analysis confirmed the diagnosis of Li-Fraumeni syndrome. The present case emphasized FDG PET/CT value of showing simultaneously multiple lesions in Li-Fraumeni syndrome, especially in the early stage without the gene analysis result.

Epidemiology and Outcomes of Neonatal Hemophagocytic Lymphohistiocytosis

OBJECTIVES

Neonatal hemophagocytic lymphohistiocytosis (HLH) is a rare entity. The objective of the study was to describe the prevalence, clinical characteristics, interventions and outcomes of neonates diagnosed with HLH in the United States.

METHODS

A retrospective analysis of 2009, 2012, and 2016 Kids' Inpatient Database was performed. Neonates discharged/died with a diagnosis of HLH were identified and analyzed.

RESULTS

Among 11,130,055 discharges, 76 neonates had a diagnosis of HLH. Fifty-two percent (95% CI: 38.6-63.6) were males and 54% (95% CI: 39.7-68.5) were white. Herpes simplex infection was present in 16% (95% CI: 9.2-28.1). 24.4% (95% CI: 14.5-37.9) received chemotherapy, 11.5% (95% CI: 5.2-23.6) IVIG and 3.6% (95% CI: 0.8-14.4) allogenic hemopoietic stem cell transplantation. Organ dysfunction was commonly seen and severe sepsis was documented in 26.6% (95% CI: 16.4-39.9). Median LOS was 16 (IQR 7-54) days. The mortality was 42% (95% CI: 30.8-55).

CONCLUSIONS

HLH is a rare diagnosis and carries a high mortality in neonates. Herpes simplex virus is the most common infection associated with neonatal HLH. HLH should be considered in the differential diagnosis in neonates presenting with multi-organ dysfunction or sepsis.