Case Study: Circumscribed Myositis Ossificans of Masseter Muscle Causing Trismus


This article discusses an interesting case report of circumscribed myositis ossificans of the masseter muscle causing trismus with a review of literature on the subject. This rare disorder is characterized by dystrophic calcification leading to heterotopic ossification (presence of bone tissue where it is not usually present) of intramuscular connective tissue. Muscles of mastication are commonly involved in this condition.


Myositis ossificans involving the masseter muscle is rather rare. This condition is characterized by dystrophic calcification and heterotopic ossification of intramuscular connective tissue. Masticatory muscles are commonly involved.

Types of myositis ossificans:

Myositis ossificans progressiva – This is a rare congenital condition characterized by malformations involving great toes and progressive heterotopic ossification 1. Spontaneous mutation tends to be the cause of most of these cases. Genetic transmission is autosomal dominant 2.

Myositis ossificans circumscripta – This condition is largely limited to a single muscle and normally one of mastication. This is generally caused by progressive ossification of intramuscular hematoma, which could occur due to a muscle injury. This term is used to classically describe non-hereditary forms of myositis ossificans.

Pseudomalignant myositis ossificans – This is limited to soft tissue not associated with trauma. This condition can be mistaken for a malignant lesion but can also be ...

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