The Role of 18F-NaF PET/CT imaging in diagnosis and management of familial tumoral calcinosis – A pictorial review

Introduction: Hyperphosphatemic familial tumoral calcinosis (HFTC) is a rare and disabling cause of hyperphosphatemia and ectopic calcifications. The aim of this educational exhibit is to familiarize clinicians with ¹⁸F-sodium fluoride (¹⁸F-NaF) PET/CT imaging manifestations of familial tumoral calcinosis (FTC). Given the rarity of the disease, it is important for clinicians to be familiar with the presentation in order to be able to diagnose FTC in clinical practice.

Background: FTC is a rare disease resulting from deficiency or resistance to fibroblast growth factor 23 (FGF23), a phosphate-regulating hormone. Patients usually present with hyperphosphatemia, ectopic calcifications in periarticular soft tissues and hyperostosis (cortical hypermineralization and patchy medullary cavity sclerosis) over the diaphyseal regions of the long bones. Additionally, it may present with systemic inflammation, ocular manifestations and dental pathology. Diagnosis of FTC is based on characteristic clinical presentation, laboratory findings, histopathology and imaging. Radiographs of lesions can show heterogeneous calcified masses while CT can be used to qualitatively monitor changes in size of ectopic calcifications and identify vascular calcifications. ¹⁸F-NaF PET/CT provides a novel avenue for superior detection and temporal quantification of ectopic calcifications and vascular involvement earlier in the disease course.

Methods: A scoping review of the literature was performed. Images from patients diagnosed with FTC and enrolled in a natural history study at our institution were utilized for the pictorial review to demonstrate the breadth of clinical presentations among a cohort consisting of 17 patients, which is among the largest available, as well as select instructive cases from the literature to present the most comprehensive pictorial of this rare disease.

Results: This review of the literature will provide:

An overview of FTC diagnosis and management

Pathogenesis of FTC

Clinical phenotype

Laboratory findings and current state of diagnosis

Differential diagnosis for Hyperphosphatemic Familial Tumoral Calcinosis

Management strategies

Role of 18F-NaF PET/CT imaging in diagnosis and prognostication of FTC

Imaging presentation of FTC

X-ray findings

Tumoral calcinosis, hyperostosis and dental x-rays

CT findings

Tumoral calcinosis

Vascular calcification

¹⁸F-NaF PET/CT features of FTC

Conclusions: It is important for nuclear medicine physicians and radiologists to be aware of this rare disease in order to enable earlier diagnosis and avoid missed diagnosis. The combination of clinical history, laboratory findings and imaging can aid in the diagnosis and management of familial tumoral calcinosis. ¹⁸F-NaF PET/CT imaging provides a novel tool for disease monitoring in FTC, and this review will serve as a resource for clinicians to identify key features of this disease on imaging.

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