Intraosseous tophaceous pseudotumor in the trigonal process of the talus.

Primary gout with destructive tophaceous pseudotumor development rarely occurs in juvenile patients with asymptomatic hyperuricemia. An expansile, intraosseous tophaceous pseudotumor on the posterior process of the talus was verified in a 14-year-old boy with posterior ankle impingement and asymptomatic hyperuricemia. A review of the literature found no similar cases had been reported. The pathogenesis of this intraosseous tophaceous pseudotumor on the trigonal process probably was caused by the penetration of urate crystals from the periosteum into the posterior process of the talus. However, the time that this intraosseous tophaceous pseudotumor developed probably was close to the time that the second ossification center of the talus fused to the talus. Thus, it cannot be ruled out that the intraosseous tophaceous pseudotumor had formed during the fusion process of the second ossification center as a possible pathogenic mechanism in this unusual case.