For more information on this topic, please read Dr. Kitterman's article, Iatrogenic Harm Caused by Diagnostic Errors in Fibrodysplasia Ossificans Progressiva.
Three of the most common misdiagnoses for FOP have been reported to be: cancer, aggressive juvenile fibromatosis, and fibrous dysplasia.
There are also many critical differences between FOP and the conditions listed above. The key to diagnosing FOP is being aware of the condition, understanding the association with the malformed toe, and also being aware of the nature of how FOP progresses. An astute clinician knowledgeable about FOP can diagnose the condition even before bone forms just from the presence of the malformed great toes and the rapidly appearing soft tissue swellings that form in characteristic anatomic locations.
One of the goals of the FOP community is to better educate physicians and healthcare workers around the world about the proper diagnosis of FOP so that dangerous misdiagnoses of FOP will not occur in the future.