"Since the process of heterotopic ossification is quite unique, differential diagnosis on a long term basis is quite limited. However, for punctual abnormalities, the following differential diagnosis should be considered:"
"C2-C7 facet joint fusion"
"Fibrodysplasia ossificans progressiva (FOP), previously known as myositis ossificans progressiva (MOP) and also known as Münchmeyer disease and stone man disease (though, as below, there is no sex predilection), is a rare, inherited disorder characterised by progressive fibrosis and ossification of muscles, tendons, fasciae, aponeuroses, and ligaments of multiple sites. It is disabling and ultimately fatal."
"Fibrodysplasia ossificans progressiva is a very rare disease, with an estimated prevalence of ~1 per 2 million. There is no racial/ethnic, or gender predilection 3. The process and symptoms of heterotopic ossification start between 2 and 5 years old."