A swollen index finger as a presentation of thyroid dermopathy.

A 68-year-old man presented with his left index finger swollen at the proximal interphalangeal joint (Picture 1A). He noticed palpitation, tremor and weight loss 3 months previously. At presentation, atrial fibrillation, pretibial myxedema, exophthalmos, diplopia on upgaze, but not fingernail clubbing were noted. Thyroid function tests were indicative of hyperthyroidism, leading to a diagnosis of Graves’ disease. Radiographs of the finger demonstrated a soft tissue swelling but not bone lesions or periosteal reactions (Picture 1B). Skin biopsy samples from the lesion disclosed widely spaced collagen and extensive mucin deposition as identified by alcian blue staining (Picture 1C). These features were consistent with thyroid dermopathy (1). The skin lesion did not cause any complaints without treatment. The same finger had been injured 20 years previously (Picture 1A, arrow). Trauma is a precipitating factor of thyroid dermopathy (2) and may explain why the skin lesion developed in his finger in addition to the pretibial area.