msk

Question 1

Achondroplasia

Answer 1

Common dysplasia characterized by abnormal bone formation at growth plate.

• Autosomal dominant (homozygous forms fatal, patients with heterozygous form have normal life span).

DWARFISM Rhizomelic dwarfism: short limbs (particularly proximal segments of femurs, humerus)

HANDS

• Short and stubby fingers (bullet-shaped) • Trident hand

SPINE

• Short interpedicular distance (typical) The interpedicular distance narrows distally
• Spinal stenosis is due to short pedicles.

PELVIS

• “Ping-pong-paddle” pelvis Rounded iliac bones Champagne pelvis Horizontal acetabular roofs

SKULL

• Skull Small skull base (enchondral ossification) and small foramen magnum
• Normal-sized calvarium (membranous ossification): frontal bossing Basilar invagination