Age / Sex : 29 / M

Age / Sex : 29/M

Chief complaint : Multiple joint contracture (gradual development over 6 years)

Myositis Ossificans progressiva (= fibrodysplasia ossificans progressiva)

Discussion

Findings:

Bilateral Hallux valgus, Short both 1^st metacarpals and both 1^st & 4^th metatarsals, Bilateral Phalangeal synostosis (monophalangeal great toe)

extensive interspinous,supraspinous lig. ossification

exuberant soft tissue ossification at Lt. scapula~ supraspinous ossification at Lt. lower trunk

Rt. prox. tibial metaphyseal pseudoexostosis

Soft tissue ossification at Rt. Distal humerus post. aspect

Diagnosis:  

Myositis Ossificans progressiva (= fibrodysplasia ossificans progressiva)

Discussion:

•         Epidemiology/Etiology/clinical manifestation

- Extremely rare (1/10million) AD disorder characterized by skeletal malformation and progressive, disabling heterotopic osteogenesis

-  Excessive stimulation of bone morphogenic protein 4 and its mRNA

-  Painful lumps and stiffness in the adjoining joint. Lumps decrease in a few weeks, but joint mobility reduction persists.

-  Exacerbating factors for ossifications at new sites includes sometimes very minor trauma, such as vein puncture, biopsy of lumps, IM injections, dental treatments, and excision of masses.

-  Ossification progresses from proximal to distal and cranial to caudal.

: Variations in bone maturation sequence

: Increased incidence of enchondromas

•         Consideration in management and prognosis

- Once diagnosis is established, usually clinically, any surgical biopsy is contraindicated.

-  Early death is inevitable d/t respiratory failure with chest wall contracture, starvation with ossification of masseter muscles. 

•          Radiographic findings

- The first radiographic finding is a soft tissue mass. The lesion gradually shrinks in size and ossifies. The final appearance of the lesion may be that of a cylindrical column of solid new bone replacing the entire muscle of the neck or extremities.

- The zonal phenomenon, characteristic of myositis ossificans cirvumscripta, is not present in progressive case.

- Ossification progresses from proximal to distal and cranial to caudal.

: Digital anomalies are present at birth

Hallux valgus, short metacarpals and metatarsals, Phalangeal synostosis (eg, monophalangeal great toe)

: Vertebral fusions, vertebral anomalies (ie, small bodies), pedicle thickening

: Ossification of inter and supraspinous ligament

: Broad, short femoral neck

: Bilateral thickening of medial cortex of tibia

        - MRI findings depend on the age of the lesion.

: In immature lesions, T2-weighted spin-echo images are associated with a homogeneous soft tissue mass with increased signal intensity. Surrounding edema may be seen in lesions less than a few months old. In T1-weighted images, only mass effect may be noted with displacement of fascial planes.

: Mature lesions appear as inhomogeneous masses with fatlike signal intensity on both T1- and T2-weighted images.

Differential diagnosis

 Metastatic calcification

 Systemic diseases related to multicentric area of myositis ossificans circumscripta including tetany, paraplegia, and burns.

References:

 D. Resnick. Diagnosis of Bone and Joint Disorders. 4^th Ed. Saunders Press, 2002: 4409-4415