ABSTRACT
An eleven year old boy presented with localized swelling of the left calf which had been developing for more than 5 years. Another smaller mass was found in the pretibial area. There was an invincible equinus deformity of the foot. Surgical biopsies revealed characteristic histological features of focal myositis showing necrotic and regenerating muscle fibers, randomly distributed, with inflammatory infiltration. An intense fibrotic reaction was observed. This constitutes to our knowledge the first reported case of focal myositis in which development of muscle sclerosis was so important that it was necessary to perform tenotomies one year after excision of the principal tumor in order to restore normal gait. A nearly two-years follow-up does not give evidence of recurrent lesion.