MON-805 - Skeletal Fluorosis Mimicking Diffuse Osteoblastic Metastatic Disease: A Case Report

Case Presentation
A 31-year-old man with a history of type 2 diabetes mellitus, beta thalassemia minor, iron deficiency anemia, and obesity presented for evaluation of weight gain. He reported weight gain of 100 pounds and night sweats over the preceding months, along with joint and muscle aches. Further history revealed many prior fractures, including bilateral ankles, right patella, right hip, multiple finger fractures, and multiple rib fractures, many with limited trauma. Possible hypercortisolism was excluded via normal dexamethasone suppression and midnight salivary cortisol levels. On further review of his medical record, diffuse bony sclerotic lesions in the axial and appendicular skeleton were noted on CT abdomen and pelvis with IV contrast. These were new as compared to a study 10 months prior. Prior to endocrine evaluation, he was seen by oncology, who ordered a PET CT. Results showed sclerotic bony structures, with diffuse activity scattered throughout and SUV values extending to 5. Given concern for diffuse metastatic disease, biopsy was obtained from bone marrow and right iliac bone, showing reactive remodeling bone and hematopoietic bone marrow, with no evidence of malignancy.
After his initial endocrine evaluation, testing showed serum fluoride elevated to 76.9 mcmol/L (reference range: < 4.1 mcmol/L). Home water testing showed normal fluoride levels. On further questioning, the patient reported significant exposure to automobile cleaning products, likely containing hydrofluoric acid, which is a common component used for brightening aluminum and cleaning roadway residues. He admitted not using protective gloves, likely causing his hyperfluorosis. A follow-up 16 months after the initial visit showed decreasing serum fluoride levels, but no interval change on PET/ CT scan.

Discussion
Skeletal fluorosis can result from fluoride exposure from multiple pathways, including accidental environmental exposure, occupational exposure, or intentional inhalant abuse. A critical diagnostic challenge in occupational cases lies in obtaining an accurate exposure history. Absorbed fluoride promotes the formation of fluorohydroxyapatite in bones, altering bone structure and causing infiltration of tendons, ligaments, and muscles by mineral deposits [1]. Clinical manifestations range from vague muscle aches, joint pain, and stiffness to skeletal deformities and neuroradiculopathy. Some cases are asymptomatic with incidentally detected skeletal fluorosis, such as our case. Radiographically diffuse otosclerosis and ossification of ligaments and tendons is often seen. Diagnosis is confirmed by elevated serum and urine fluoride levels. Treatment involves symptom management and cessation of exposure.

References
1. Sellami M, et al. Skeletal fluorosis: don’t miss the diagnosis. Skeletal Radiol. 2020;49:345–57.

*Unless otherwise noted, all abstracts presented at ENDO must not be released to the press or the public until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.*