What are the other Names for this Condition? (Also known as/Synonyms)

• MOC (Myositis Ossificans Circumscripta)
• Myositis Ossificans Traumatica

What is Myositis Ossificans Circumscripta? (Definition/Background Information)

• Myositis Ossificans Circumscripta (MOC) is a benign bony tumor that is caused by formation of bone in soft tissue, in an area of injury/trauma. It can occur anywhere in the body, wherever an injury occurs, but is frequently seen in the limbs or shoulder
• The condition may occur in individuals of any age. However, participation in high-impact sports or undergoing certain surgical procedures may place some individuals more at risk than the others
• In majority of cases, MOC occurs within a muscle, which is termed Intramuscular Myositis Ossificans Circumscripta. The tumors may grow rapidly and can raise concerns of malignancy. MOC may be diagnosed through radiological studies and tissue biopsy
• Complications associated with the condition include cosmetic issues and restricted movement of joints, if they occur in the vicinity of a joint
• Myositis Ossificans Circumscripta cannot be effectively prevented. The treatment involves a surgical removal of the tumor. The prognosis with appropriate treatment is excellent, but the condition may recur

Who gets Myositis Ossificans Circumscripta? (Age and Sex Distribution)

• Myositis Ossificans Circumscripta is a rare condition that may affect individuals of any age
• There are no known ethnic, racial, or gender patterns associated with MOC; the condition is observed worldwide

What are the Risk Factors for Myositis Ossificans Circumscripta? (Predisposing Factors)

The most important risk factor for Myositis Ossificans Circumscripta is trauma or injury. This may occur due to:

• Participation in high-impact contact sports resulting in injuries
• Surgical procedures performed for various health conditions
• Any injury to the soft tissue and muscle

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Myositis Ossificans Circumscripta? (Etiology)

• Myositis Ossificans Circumscripta is caused by an abnormal reaction of the body to a trauma
• The trauma or injury may occur from sports, during a surgery, or from other factors
• In some cases, certain genetic mutations have been observed, but they have not been well-established

What are the Signs and Symptoms of Myositis Ossificans Circumscripta?

The signs and symptoms associated with Myositis Ossificans Circumscripta include:

• Formation of a benign tumor-like lump in the affected region
• The tumor appears as a hard mass (bony tumor); calcification is noted in the tumor
• The size of the tumor may range from 1 cm to up to 10 cm
• The tumor may occur anywhere in the body, but is usually seen in the arms, legs (thigh), and shoulder
• There may be a period of rapid growth, which can lead to the suspicion of cancer

How is Myositis Ossificans Circumscripta Diagnosed?

The diagnostic procedures used for Myositis Ossificans Circumscripta may include:

• Complete evaluation of medical history along with a thorough physical exam
• Blood tests: It may show elevated levels of alkaline phosphatase and bone specific alkaline phosphatase
• Imaging studies such as x-rays, CT, and MRI scans
• Open biopsy or core biopsy of tumor: A tissue biopsy is performed and sent to a laboratory for a pathological examination. A pathologist examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis. Examination of the biopsy under a microscope by a pathologist is considered to be gold standard in arriving at a conclusive diagnosis

Note: A needle biopsy may not be helpful, because one may not be able to visualize the different morphological areas of the tumor. Hence, a needle biopsy as a diagnostic tool has certain limitations, and an open surgical biopsy is preferred.

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Myositis Ossificans Circumscripta?

The complications associated with Myositis Ossificans Circumscripta include:

• Decreased mobility and limitation of movement of the affected joint, if the tumor occurs near a joint
• Some individuals may have cosmetic concerns and may seek surgical removal of the tumor
• Recurrence of MOC

How is Myositis Ossificans Circumscripta Treated?

The treatment measures available for Myositis Ossificans Circumscripta include:

• The treatment is a complete surgical excision (an excisional open biopsy is the preferred method of removal), which can result in a cure
• In some cases, the healthcare provider may recommend a ‘wait and watch’ approach
• Follow-up care with regular screening and check-ups are important and encouraged

How can Myositis Ossificans Circumscripta be Prevented?

• Currently, there are no specific methods or guidelines to prevent Myositis Ossificans Circumscripta
• The use of suitable protective safety gear while participating in high-risk sports can help avoid injuries to some extent

What is the Prognosis of Myositis Ossificans Circumscripta? (Outcomes/Resolutions)

Myositis Ossificans Circumscripta is a benign condition that occurs as a response to an injury. With adequate treatment, the prognosis is generally excellent.

Additional and Relevant Useful Information for Myositis Ossificans Circumscripta:

Myositis Ossificans Circumscripta is related to fibrodysplasia ossificans progressive (FOP), an extremely rare and debilitating genetic disorder.