Surgical excision of heterotopic ossification of hip in a rare case of Moyamoya disease with extra articular ankylosis

We report a case of isolated ossification of iliopsoas with ankylosis of the left hip in a 27-year-old female. The patient was diagnosed to have Moyamoya disease, a rare chronic occlusive disorder of cerebrovascular circulation following an acute onset of hemiplegia. The patient presented 9 months later to us with ankylosis of left hip which was successfully treated by surgical excision of the heterotopic bone and there was no recurrence at the end of 5 years. A review of literature failed to reveal a similar case with isolated and complete ossification of iliopsoas muscle associated with Moyamoya disease which required surgical intervention. Surgical excision resulted in dramatic improvement in the quality of life. Surgical excision of neurogenic type of heterotopic ossification is a very successful procedure and timely intervention after maturity of mass is very important to prevent the onset of secondary complications and to avoid recurrence.