What are the physical characteristics of Hypochondroplasia?

Due to its mild nature, it is often times difficult to differentiate between “familial” shortness of stature and hypochondroplasia. Hypochondroplasia seems to be the grey area between achondroplasia and being constitutionally shorter than average. The average adult height of hypochondroplastic patient varies between 52 and 58 inches.

Face and Skull:

• Average head circumference or slight macrocephaly
• Slightly prominent forehead

Trunk, Chest and Spine:

• Long trunk, as compared to short extremities
• Protuberant abdomen
• Anteroposterior shortening of pedicles in the lumbar region of the spine
• Spinal stenosis
• Possible lumbar lordosis

Arms and legs:

• Short and stocky limbs
• Mild genu varus in infancy
• Ligamentous laxity with limited elbow extension and supination
• Broad and short hands without trident formation
• With age, prominent aching knees, elbows, and ankles

What are the x-ray characteristics?

The major radiographic features of hypochondroplasia include narrowing of interpediculate distances with anterioposterior shortening of pedicles. Vertebral bodies in lumbar region of spine have increased dorsal concavity. The height of the vertebral bodies is normal. The deformities of the spine, however, are not as pronounced as in the case of achondroplasia.

The pelvis is square with short ilia, although the flare of the iliac crests is normal. The sacrum is hypoplastic and low set on the iliac bones, effectively narrowing the transverse diameter of the pelvis. The tubular bones are short and with mild metaphyseal flare (most evident at the knees). The styloid processes of the ulnae are frequently long. Femoral necks are short and broad. Distal fibulae are long in comparison to tibia. In children, growth plates of distal femurs exhibit a shallow, V-shaped indentation. This is due to slower enchondral bone growth at the center of the growth plate as compared to growth at the periphery. Again, this change is more mild in hypochondroplasia than in achondroplasia. Generalized brachydactyly is mild to moderate. Occasionally, the neurocranium is slightly larger.

• What are the physical characteristics of Hypochondroplasia?
• How is the diagnosis made?
• Problems in the musculoskeletal system
• Problems elsewhere in the body
• What are things to watch out for?
• References