Thyroid acropachy is a triad consisting of digital clubbing, soft tissue swelling of the hands and feet, and periosteal new bone formation. It is a rare manifestation of thyrotoxicosis with an incidence of 0.1–1% of patients with Graves disease. Thyroid acropachy is usually associated with exophthalmos and pretibial myxedema.

The first, second, and fifth metacarpals, the proximal phalanges of the hand, and the first metatarsal and proximal phalanges of the feet are most commonly affected.

In addition to thyroid acropachy, patients with thyrotoxicosis can develop a characteristic onycholysis in which the free edge of the nail is undulated and curved upward (Plummer nails). The fourth fingernails are initially involved. The nails are fragile, and the nail bed of the toes may be hyperpigmented.