Scurvy

Introduction

• Scurvy is disease that results from vitamin C deficiency
• Vitamin C (ascorbic acid) deficiency causes failure of collagen synthesis and osteoid formation
• Results in osteoporosis and possibly spontaneous bleeding

Pathogenesis

• Normal collagen synthesis depends upon the hydroxylation of proline and lysine for which vitamin C acts as a cofactor
  • Vitamin C deficiency prevents hydroxyproline and hydroxylysine formation
  • Produced collagen contains only 'non-hydroxylated' proline and lysine
  • The resulting collagen fibrils lack hydrogen bonding and lose mechanical stability
• Bony pathogenesis consists of two parts
  • Failure to lay down bony matrix
  • Persistence of an unabsorbed calcified cartilage lattice
• Cartilage cells of the epiphyseal plate multiply and orientate themselves normally 
• Intervening matrix becomes calcified, but osteoblasts fail to lay down osteoid
• Calcified cartilaginous matrix is not completely resorbed
• Epiphyseal plate becomes widened and irregular
• Spicules of calcified cartilage fracture and a very irregular radiologically dense zone arises at the junction of epiphysis and shaft
• Failure of resorption of calcified cartilage also makes ring sign

Natural History

• Onset at 6 months - 2 years
• Rare in adults

Clinical Presentation

• Infants are irritable and anaemic
• Gums may bleed spontaneously
• Haemorrhage near large joints may cause excruciating pain and tenderness
• Fractures or epiphyseal separation may occur 

Imaging and Diagnostic Studies

• Generalised bone rarefaction
• Most marked in metaphyses of the long bone which may be deformed or fractured
  • Metaphyseal lucency (Trummerfeld Zone)
  • Metaphyseal corner fractures through the weakened lucent parts (Pelkan spurs) results in cupping of the metaphysis
• Normal calcification in growing cartilage produces dense transverse bands :
  • At juxta-epiphysial zones (Frankel white line) 
  • Around ossific centres of the epiphyses (Wimbergers ring sign)
• Zones of provisional calcification appear dense
• Subperiosteal haematomas appear as soft tissue swellings or peri-osseous calcification 

Treatment

• Large doses of vitamin C bring prompt relief