Onset: after >18 months following surgical / radioactive ablation of thyroid gland for hyperthyroidism (does not occur with antithyroid medication)

Frequency: 0.5–1% of patients with thyrotoxicosis

• clubbing, soft-tissue swelling, NO pain
• eu- / hypo- / hyperthyroid state

Location: metacarpals + phalanges of hand; less commonly feet, lower legs, forearms

• thick spiculated lacy “feathery” periosteal reaction in an asymmetric distribution; mostly on radial aspect of bone

DDx:

1. Pulmonary osteoarthropathy (painful)
2. Pachydermoperiostosis
3. Fluorosis (ligamentous calcifications)