For unknown reasons, children born with<unk>  often have malformed big toes, sometimes missing a joint or, in other cases, simply presenting with a notable lump at the minor joint. The first "flare-up" that leads to the formation of<unk>  bone usually occurs before the age of 10. The bone growth generally progresses from the top of the body downward, just as bones grow in fetuses. A child with<unk>  will typically develop additional bones starting at the neck, then at the shoulders, arms, chest area, and finally at the feet. Specifically, ossification is typically first seen in the dorsal, axial, cranial and proximal regions of the body. Later the disease progresses in the ventral, appendicular, caudal and distal regions. However, it does not necessarily occur in this order due to injury-caused flare-ups. Often, the tumor-like lumps that characterize a flare-up of the disease appear suddenly. Bone growth occurring during flare-ups may result in the loss of mobility to affected joints, including, if the jaw/mandible is involved, the inability to fully open the mouth, limiting speech and eating. A specific occurrence of a flare-up of this condition in the foot/ankle joints can result in the limited ability to put a foot flat on the ground. Bone growth can also result in the immobilization of the hip or knee, affecting the individual's ability to walk. Extra bone formation around the rib cage restricts the expansion of lungs and diaphragm causing respiratory complications. Since the disorder is so rare, the condition may be misdiagnosed as cancer or fibrosis. This leads physicians to order biopsies which can exacerbate the growth of<unk>  bone. The presence of malformed toes or thumbs in those born with<unk>  help distinguish this disorder from other skeletal problems. With proper medical management the median age of survival is 40 years. However, delayed diagnosis, trauma, and infections can decrease life expectancy.
Fibrodysplasia ossificans progressiva
Fibrous dysplasia of bone
Myositis ossificans
Langer–Giedion syndrome
Gerodermia osteodysplastica
Osteitis fibrosa cystica
Enchondromatosis
Osteoma cutis