MYOSITIS OSSIFICANSBY: DR. SHAMAILA SHUJA

ABBASI SHAHEED HOSPITAL, KARACHI

MYOSITIS OSSIFICANS

• BENIGN PROCESS CHARACTERIZED BY HETEROTOPIC BONE (SOME TIMES CARTILAGE) FORMATION IN MUSCELS, TENDONS & FACIA.

CLINICAL FEATURES

• RESTRICATIONS OF MOVEMENT RANGE• PAIN IN MUSCELS ON USE• HARD LIMP IN THE MUSCEL

TYPES

(1) PROGRESSIVE TYPE

(MO-CONGENITA)

(2)POST TRAUMATIC(MO-CIRCUMSCRIPTA)

(3)PARAPLEGIC

MYOSITIS

(1) PROGRESSIVE TYPE

(MO-CONGENITA)1) AUTOSOMAL DOMINANT2) MORE IN BOYS3) APPEARS WITHIN ONE YEAR AS OSSIFICATION OF PERIMUSCULAR FACIA4) ASSOCIATED WITH OTHER CONGENITAL BONE LESIONS SUCH AS PHALANGEAL &

METACARPAL HYPOPLASIA OF THUMB & BIG TOE5) INITIALLY ILL DEFINED HAZY CALCIFICATION OF SOFT TISSUE OVER BACK & NECK

WITH SOFT TISSUE MASSES6) LATER BONY MASSES RESOLVE IRREGULAR PLATES ARE FORMED WITH

ANKYLOSED JOINTS. IT IS USUALLY FATAL

PROGRESSIVE TYPE(MO-CONGENITA)

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PARASPINAL

PROGRESSIVE TYPE

(MO-CONGENITA)

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PROGRESSIVE TYPE

(MO-CONGENITA)

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PROGRESSIVE TYPE

(MO-CONGENITA)

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POST TRAUMATIC(MO-SIRCUMSCRIPTA)

• USUALLY SEEN AFTER TRAUMA• A WARM PAINFUL LESION IN THE FORM OF SOFT TISSUE MASS / HAEMATOMA FORMS DURING FIRST TWO

WEEKS. FLUID-FLUID LEVEL & MARKED ENHANCEMENT WITH GADOLINIUM INJECTION SEEN• IN SUBSEQUENT TWO WEEKS AMORPHOUS DENSITIES DEVELOP IN THE MASS, POSSIBLY WITH

PERIOSTEAL REACTION. IN THESE FOUR WEEKS MRI CAN NOT DISTINGUISH BETWEEN MO & PAROSTEAL OSTEOSARCOMA. CENTRAL & PERIPHERAL BIOPSY IS REQUIRED. HOWEVER, IN ACUTE AND INTERMEDIATE STAGES OF MO (LESS THAN 8 WEEKS) THERE IS MARKED SURROUNDING OEDEMA WHICH IS UNUSUAL IN CASE OF SOFT TISSUE SARCOMAS

• LATER THE MASS MATURES (OSSIFIES) IN PERIPHERAL TO CENTRAL PATTERN AND DECREASES IN SIZE• BRACHIALIS & QUADRICEPS ARE PARTICULARLY PRONE• SOFT TISSUES AROUND THE ELBOW AND THIGHS ARE THE COMMON SITES

POST TRAUMATIC(MO-CIRCUMSCRIPTA)

POST TRAUMATIC(MO-CIRCUMSCRIPTA)

POST TRAUMATIC(MO-CIRCUMSCRIPTA)

PARAPLAGIC MYOSITIS

• DEVELOPS IN PARAPLAGICS WITHIN 3 – 4 WEEKS BELOW THE LEVEL OF PARALYSIS

• HETEROTROPIC PERIARTICULAR CALCIFICATION & OSSIFICATION AROUND THE JOINTS SEEN PARTICULARLY THE HIP WITH IRREGULAR BONE FORMING PLAQUES ON X-RAY

PARAPLAGIC MYOSITIS