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What is POH?
Introduction
to POH
Progressive Osseous
Heteroplasia (POH) is a rare genetic condition in which the body
makes extra bone in locations where bone should not form. Extra
bone develops inside skin, subcutaneous tissue (fat tissue beneath
the skin), muscles, tendons, and ligaments. This ”out of
place extra bone formation” is commonly referred to as heterotopic
ossification. In people with POH, nodules and lace-like webs of
extra bone extend from the skin into the subcutaneous fat and
deep connective tissues, and may cross joints. Extra bone formation
near the joints leads to stiffness, locking, and permanent immobility.
Symptoms
of POH
The condition is often
first noted in infancy with the appearance of small “rice-grain”
particles of bone in the skin. A parent may describe this as a
roughness in the skin. During childhood, bone formation may progress
from the skin into subcutaneous tissue and extend into deeper
structures including muscles, tendon and ligament. Affected areas
may be small or large and involve scattered and variable regions
of the body surface. The condition does not involve any other
organ system and does not affect the formation of any portions
of the normal skeleton at birth.
POH is often
congenital, meaning that it may be present at birth. In most children
symptoms of POH usually begin during the first few months of life.
The majority of affected children are diagnosed with POH before
the age of ten.
Bone formation
begins typically in small patches of skin and can occur in any
region of the body. People who have POH experience different rates
of new bone formation: in some, the progress is rapid, while in
most it is more gradual. In each child, the exact rate of progression
is unpredictable. In any affected area, there appears to be a
progression from superficial to deeper tissues. For example, extra
bone formation occurs first in the skin, then progresses down
to subcutaneous tissue, and then to deeper tissues like muscle.
In some individuals, the bone formation may involve a small area
of the body, and in others, relatively large or multiple areas
of the body. Very often, the extra bone formation may predominate
more on one side of the body. Although the limbs are most commonly
affected, bone formation may also involve the head, chest, abdomen,
pelvis and back.
Solving
the Mysteries of POH
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