All are true regarding myositis ossificans progressive except -

Myositis ossificans is a misnomer as there is no inflammation in muscles (it is not a form of myositis). Myositis ossificans progressive begins in childhood, usually before the age of 6 years. There may be restrictive chest wall disease. There is fusion (ankylosis) of cervical spine. Biopsy shows edematous muscle with many inflammatory cells and fragmented myofibrils. Later, true bone forms, often in cartilage, and subsequent mineralizes.