Thyroid Acropachy

Thyroid acropachy is a rare extrathyroidal manifestation of Graves disease, with clubbing, soft tissue swelling of the hands and feet and periosteal new bone formation.

It affects roughly 1% of patients with Graves disease. Almost all also have orbitopathy and most have pretibial myxoedema (thyroid dermopathy). Smoking is a strong association.

It usually appears after treatment of hyperthyroidism, often when the patient is euthyroid or hypothyroid, and can persist or progress.

Pathophysiology.

Autoantibodies to the thyrotropin receptor probably act on fibroblasts and bone cells in the extremities, increasing glycosaminoglycan deposition and periosteal bone formation. Mechanism is not fully known.

• Digital clubbing, painless swelling of the fingers and toes, and soft tissue thickening of the hands and feet.
• Bone pain in some. Pretibial myxoedema and exophthalmos are usually present.

Red flags.

• Rapid onset of clubbing, bone pain or cough in a smoker (look for lung cancer).
• Rapidly progressing orbitopathy or dermopathy.

• Clinical diagnosis in a patient with current or past Graves disease with orbitopathy and dermopathy.
• Radiographs of the hands and feet: spiculated or lace like periosteal new bone along the diaphysis of the metacarpals, metatarsals and phalanges. Bone scan shows increased uptake.
• Thyrotropin receptor antibodies (usually high), thyroid function and a chest radiograph.

Differential diagnosis.

• Hypertrophic osteoarthropathy from lung cancer, chronic lung disease, cyanotic heart disease or biliary disease (long bones involved, painful).
• Pachydermoperiostosis (primary hypertrophic osteoarthropathy), acromegaly and psoriatic arthritis.
• Clubbing from other causes.

• No specific therapy is proven. Control thyroid function and stop smoking.
• Topical high potency glucocorticoid under occlusion for thyroid dermopathy. Analgesia for bone pain.
• Treat orbitopathy as its own disease.
• Investigate for lung malignancy and chronic cardiopulmonary disease if features suggest hypertrophic osteoarthropathy.
• Evidence is limited to case reports and small series.

Monitoring. Thyroid function and orbit review at a frequency set by Graves disease activity.

Referral and escalation. Endocrinology with ophthalmology and rheumatology if joint symptoms or severe orbitopathy.