Which congenital condition results in disproportionate short limbs due to impaired cartilage formation at the ends of long bones?

• A. Rheumatoid Arthritis
• B. Achondroplasia
• C. Rickets
• D. Vertebral Compression Fracture

Answer: (B)

Disorder of endochondral bone growth at the growth plates of long bones is what creates disproportionate limb shortening. Achondroplasia is a congenital form of dwarfism caused by a mutation that makes FGFR3 overactive, which inhibits chondrocyte proliferation in the growth plates. This disruption of cartilage formation and subsequent endochondral ossification leads to shortened proximal limbs (rhizomelic shortening) while the trunk remains relatively normal in length. Other recognizable features can include a disproportionately large head with frontal bossing and midface hypoplasia. The other options describe conditions that don’t produce this specific growth plate problem: rheumatoid arthritis is an autoimmune disease affecting joints later in life; rickets is a vitamin D–deficiency affecting bone mineralization; vertebral compression fracture is a traumatic injury to the spine. Therefore, achondroplasia best explains the described pattern.