Fibrodysplasia ossificans progressiva – A rare genetic disorder and the role of Technetium-99m methylene diphosphonate bone scan Nitin Gupta, Ankur Pruthi, Suneel Kumar, Ritu Verma, Ethel Shangne Belho Indian Journal of Nuclear Medicine 2019 34(3):209-212 Fibrodysplasia ossificans progressiva is a rare genetic disease believed to occur in approximately 1 in 2 million people worldwide and is characterized by progressive extraosseous ossification over the course of a lifetime in an inevitable and unpredictable episodic manner, with most patients being confined to a wheelchair by the third decade of life and requiring life-long care. The extraosseous calcification involves ligaments, tendons, muscles, and connective tissue leading to severe restriction of movements. Another hallmark of this condition is abnormal great toes. The diagnosis is often made on clinical and radiological examination, but Technetium-99m methylene diphosphonate (Tc-99m MDP) bone scan is usually indicated to determine the extent of the disease. We hereby present a case series comprising of four patients suffering from this debilitating illness who underwent Tc99m MDP bone scan for initial diagnosis and localizing sites of heterotopic ossification.