Mass-induced Unilateral Hallux Valgus

: Various causes of hallux valgus exist. However, mass-induced hallux valgus is a rare phenomenon. To the best of our knowledge, there has been 1 previous report on mass-induced hallux valgus in the English literature; however, that report described giant cell tumor of the extensor digitorum longus tendon sheath. We believe ours to be the first published case of osteochondroma of the second metatarsus-induced hallux valgus. A 19-year-old woman presented with pain and tenderness in the left hallux of 3 months' duration. After a diagnosis of bony mass with hallux valgus, an operative excision was performed through a dorsal approach on the first web space of the left foot. The histopathologic diagnosis was osteochondroma. One-year follow-up radiographs showed a decreased hallux valgus angle and intermetatarsal angle. Unilateral hallux valgus occurs in a mass area. After excision of the mass, hallux valgus angle and intermetatarsal angle decrease. The rotational deformity is not severe. There is little probability of discovering its etiology, but mass-like osteochondroma should be considered.