Abnormal cartilage deposits at the long bone epiphyses indicate which skeletal dysplasia?

Abnormal cartilage deposits at the long bone epiphyses indicate which skeletal dysplasia?

• A. Achondroplasia
• B. Osteogenesis imperfecta
• C. Marfan syndrome
• D. Down syndrome

Answer: (A)

Abnormal endochondral ossification at the growth plates of long bones is the key idea. In achondroplasia, a FGFR3 mutation causes a gain of function that slows chondrocyte proliferation and maturation in the epiphyseal (growth) plates. The cartilage that should be laid down at the ends of the bones becomes defective and dysregulated, so the normal process of turning cartilage into bone is disrupted. This leads to the characteristic disproportionate short stature with shortened proximal limbs and abnormal cartilage at the growth plates. Osteogenesis imperfecta involves defective collagen type I and bone fragility rather than abnormal cartilage deposition at growth plates. Marfan syndrome affects connective tissue and typically presents with long, slender bones and ligamentous features rather than primary epiphyseal cartilage abnormalities. Down syndrome can have various skeletal findings, but not the specific pattern of abnormal cartilage deposition at long bone epiphyses seen in achondroplasia.

Abnormal endochondral ossification at the growth plates of long bones is the key idea. In achondroplasia, a FGFR3 mutation causes a gain of function that slows chondrocyte proliferation and maturation in the epiphyseal (growth) plates. The cartilage that should be laid down at the ends of the bones becomes defective and dysregulated, so the normal process of turning cartilage into bone is disrupted. This leads to the characteristic disproportionate short stature with shortened proximal limbs and abnormal cartilage at the growth plates.

Osteogenesis imperfecta involves defective collagen type I and bone fragility rather than abnormal cartilage deposition at growth plates. Marfan syndrome affects connective tissue and typically presents with long, slender bones and ligamentous features rather than primary epiphyseal cartilage abnormalities. Down syndrome can have various skeletal findings, but not the specific pattern of abnormal cartilage deposition at long bone epiphyses seen in achondroplasia.