Achondroplasia
What is achondroplasia?
Achondroplasia is a genetic (inherited) condition that results in abnormally short stature. All persons with achondroplasia are little people. The average height of an adult with achondroplasia is 131 cm (52 inches, or 4 foot 4) in males and 124 cm (49 inches, or 4 foot 1) in females.
Achondroplasia is the most common cause of short stature with disproportionately short limbs.
Achondroplasia is a disorder of bone growth. Although achondroplasia literally means "without cartilage formation," the problem in achondroplasia is not in forming cartilage but in converting it to bone, particularly in the long bones.
Achondroplasia is one of the oldest known birth defects. The frequency of achondroplasia is estimated to range from about 1 in 10,000 births in Latin America to about 12 in 77,000 in Denmark. An average figure worldwide is approximately 1 in 25,000 births.
What are the characteristics of achondroplasia?
Achondroplasia is a distinctive condition that usually can be noted at birth. The baby with achondroplasia has a relatively long, narrow torso (trunk) with short extremities (arms and legs) and a disproportionate shortening of the proximal (near the torso) segments of the limbs (the upper arms and thighs). There is a typically large head with prominence of the forehead (frontal bossing), underdevelopment (hypoplasia) of the midface with cheekbones that lack prominence, and a low nasal bridge with narrow nasal passages. The baby's fingers appear short and the ringer and middle fingers diverge giving the hand a trident (three-pronged) appearance. Most joints can extend more than normal. For example, the knees can hyperextend beyond the normal stopping point. Not all joints are lax in this way. To the contrary, extension and rotation of the elbow are abnormally limited. Hip extension also tends to be limited.
At birth there is often prominence of the mid-to-lower back with a small gibbus (a hump). With walking, the hump goes...
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