Myositis ossificans progressiva

A 23-year-old man with myositis ossificans progressiva was seen in the orthopaedic clinic with pain on sitting as a result of a bony spur extending caudally from the right ischiopubic eminence. The fragment of bone was mobile and exquisitely tender on palpation. There was a recent history of falling out of bed which was thought to be relevant to its onset. A pelvic radiograph (Figure 1a) showed an ischiopubic spur in conjunction with a substantial ischiofemoral bar that had effectively fused the right hip. He also had ectopic ossification deformities of the spine, left shoulder (Figure 1b) and thoracic cage (Figure 1c).

He initially presented at 6 years of age with a palpable exostosis of the proximal right tibia. Over the next 3 years he developed several haematomas with subsequent calcification often following minor trauma. By the age of 9 years, at which time the diagnosis was made, calcification was present at multiple sites and corresponding joint mobility was reduced. A maternal history of Addison's disease had prompted the exclusion of autoimmune disorders. Repeated coagulation screens were also normal. The diagnosis was eventually made on the basis of short hypoplastic halluxes (Figure 2) which are the classical dysmorphic markers of this condition. This was supported by biopsy, the tissue showing features of fibroblastic proliferation. Unfortunately the biopsy site was further affected by ossification. He was commenced on a course of etidronate and physiotherapy.

It was decided to proceed with limited surgery to excise the ischial spur. The patient accepted the possibility of recurrence or exacerbation following the procedure, the rationale being that any subsequent ossification was unlikely to form such a sharp spur (Figure 1a). Following surgery discomfort has been dramatically reduced and he is able to sit without pain.