BACKGROUND Osteofluorosis is caused by chronic fluoride intoxication. Fluoride is used in toothpaste for the prevention of dental caries, and dental fluorosis has often been reported among children and attributed to ingestion of fluoride toothpaste. We report a case of chronic fluoride intoxication caused by excess use of toothpaste in an adult. METHODS A 45-year-old woman consulted a rheumatologist for painful swelling of the fingers, phalangeal rather than articular. She also had brown staining on her teeth. Radiography of the hands showed periosteal apposition on the phalanges. Further work-up ruled out tumoral or thyroid causes. Laboratory tests showed elevated fluoride levels in the blood (50.9 micromol/L, normal<1.5 micromol/L) and in the urine (721 micromol/L, normal<46 micromol/L). On questioning, we found only one cause for chronic fluoride intoxication: excess and unusual use of toothpaste. The patient brushed her teeth 18 times a day and swallowed the toothpaste, because she liked the taste. She consumed a tube of toothpaste every 2 days, thereby swallowing 68.5 mg of fluoride every day. Suspecting fluorosis from toothpaste, we asked the patient to use a toothpaste without fluoride. Sixteen weeks later, the pain had ceased, and laboratory tests showed massively reduced but still elevated fluoride levels in the blood (6.9 micromol/L) and urine (92.7 micromol/L). CONCLUSIONS In this rare case of fluoride intoxication, misuse of a normally innocuous product caused osteofluorosis.