An unusual case of adult onset progressive heterotopic ossification suggesting a variant form of fibrodysplasia ossificans progressiva.

Progressive heterotopic ossification (HO) is a rare disease of genetic inheritance. Fibrodysplasia ossificans progressiva (FOP) is an identified debilitating subcategory in which anomalous ossification usually begins in childhood. Congenital big toe anomalies and specific patterns of progression of ossification confirm the classic disease. Adult onset disease is extremely rare. The mechanism of disease progression is still unclear, and there is no consensus on the treatment modalities. We report a 47-year-old man with adult-onset progressive HO around the bilateral pelvic and shoulder girdles and thoracolumbar spine, which suggested a variant form of FOP. Although surgical excision is considered counterproductive in FOP, our patient showed improvement in his shoulder movement following surgery. Other management strategies, including surgery around the hips, indomethacin prophylaxis, irradiation and bisphosphonate therapy, did not improve his range of movement or disease progression.