[Fibromatosis and fibrodysplasia ossificans progressiva. An avoidable diagnostic error]

Myositis ossificans progressiva is a rare progressive disease of connective tissue and muscle whose early diagnosis, before the lesions become ossified, can be difficult. The congenital malformations that accompany the disease may help in this diagnosis.

A 12 year-old boy developed a localized swelling in the right trapezius muscle. Muscle biopsy showed fibromatosis lesions. Surgical excision was incomplete and despite chemotherapy, new lesions appeared periodically in the cervical and dorsal regions where they became ossified. Bilateral hallux valgus was noticed at that time and used to rectify the diagnosis as myositis ossificans progressiva.

Many children suffering from myositis ossificans progressiva have congenital malformations, most commonly of big toes and thumbs. These anomalies are important for distinguishing myositis ossificans progressiva from other inflammatory diseases of muscle.