A newborn with macrocephaly, poor skull mineralization, short limbs, and fractures likely has a defect in which extracellular component?

A newborn with macrocephaly, poor skull mineralization, short limbs, and fractures likely has a defect in which extracellular component?

• A. Glycosidase
• B. Sulfatase
• C. Elastin
• D. Collagen

Answer: (D)

Bone strength comes from a scaffold of organic matrix laid down by osteoblasts, with type I collagen being the main protein. This collagen-rich framework provides the structure that minerals (like hydroxyapatite) attach to and harden the bone. If collagen is defective, the matrix is weak and cannot properly support mineral deposition, resulting in bones that fracture easily and may show poor mineralization—typical of conditions affecting collagen type I. Elastin isn’t a major component of bone matrix, and defects in glycosidases or sulfatases are lysosomal storage problems involving glycosaminoglycans rather than the extracellular matrix of bone. So, a defect in the extracellular collagen that forms the bone’s organic scaffold best explains the neonatal macrocephaly, poor skull mineralization, short limbs, and fractures.

Bone strength comes from a scaffold of organic matrix laid down by osteoblasts, with type I collagen being the main protein. This collagen-rich framework provides the structure that minerals (like hydroxyapatite) attach to and harden the bone. If collagen is defective, the matrix is weak and cannot properly support mineral deposition, resulting in bones that fracture easily and may show poor mineralization—typical of conditions affecting collagen type I. Elastin isn’t a major component of bone matrix, and defects in glycosidases or sulfatases are lysosomal storage problems involving glycosaminoglycans rather than the extracellular matrix of bone. So, a defect in the extracellular collagen that forms the bone’s organic scaffold best explains the neonatal macrocephaly, poor skull mineralization, short limbs, and fractures.