LAUSR

BACKGROUND Nontraumatic myositis ossificans is a rare disease whose specific pathogenesis is unclear. Early diagnosis of this disease is very difficult in children because of difficulties in determining medical history and nonspecific early clinical manifestations, which may lead to the failure of timely and effective diagnosis and treatment in some patients. We report the diagnosis and treatment of a child with nontraumatic myositis ossificans and summarize the clinical characteristics and diagnosis and treatment of the disease. CASE SUMMARY An 8-year-old girl first came to our hospital for more than a week with pain in the right lower limb. There was no history of trauma or strenuous activities. On physical examination, no mass on the right thigh was found, and the movement of the right lower extremity was limited. Ultrasonography showed synovitis of the hip, and bed rest was recommended. Three days later, the child’s pain persisted and worsened, accompanied by fever and other discomforts. She came to our hospital again and a mass was found on the right thigh with redness and swelling on the surface. The images showed a soft tissue tumor on the right thigh with calcification. Routine blood tests revealed that the inflammation index was significantly increased. In case of infection, the patient was given antibiotics, and the pain was relieved soon after, without fever. However, the right thigh mass persisted and hardened. The patient underwent incision biopsy more than 1 mo later, and the postoperative pathology showed nontraumatic myositis ossificans. After approximately 9 mo of observation, the tumor still persisted, which affected the life of the child, and then resection was performed. Since follow-up, there has been no recurrence. CONCLUSION Due to the difficulty in discerning a child's medical history and the diverse early manifestations, it is difficult to diagnose nonossifying muscle disease in children in its early stage. Measures such as timely follow-up and periodic image monitoring are conducive to early diagnosis of the disease. The disease has a certain degree of self-limitation, and it can be observed and treated first. If the tumor persists in the later stage or affects functioning, then surgery is considered.