Clinical presentation of fibrodysplasia ossificans progressiva: pitfalls in diagnosis.

A patient presented with a rapidly growing mass in the cervicothoracic paraspinous region. Associated clinical and radiographic skeletal abnormalities and histopathologic findings showing mild to moderate proliferation of spindle cells in a myxoid stroma led to the diagnosis of fibrodysplasia ossificans progressiva. Recognizing the clinical features of this disease is important and should avoid the need for obtaining tissue to make the diagnosis, because performing a biopsy may be particularly morbid in these patients.