Osteomalacia & Rickets

  

Pathophysiology

  • Osteomalacia (or Rickets in children) describes the pathological ‘softening’ of bones which occurs due to inadequate bone mineralisation
  • It occurs as a consequence of low concentrations of calcium or phosphate, most commonly related to Vitamin D deficiency. 
  • Causes:
    • Vitamin D deficiency is the most common cause 
    • Chronic renal failure
    • Vitamin D resistant rickets 

Clinical Features

  • Children - Rickets
    • Bone pain 
    • Skeletal deformities in Rickets - knock knee, bow legs, scoliosis, thickening of ankles/wrists
    • Short height 
    • Waddling gait
    • Differential diagnosis: It is important to note that bowing of the legs can be a normal variant, up to the age of 4. It is referred to as physiologic genu varum, and should be considered in an otherwise healthy child with normal examination with good range of motion. 
  • Osteomalacia
    • Bone pain is the main feature of - especially in the back, legs and pelvis
    • Weakness
    • Fragility fractures
  • Examination findings: Bony tenderness may be present - e.g on palpation of shins etc. 

Investigations

  • Bloods: 
    • LOW: calcium, phosphate
    • HIGH: PTH (compensatory), ALP
    • X-rays - Looser zones - cracks that appear in the bones
    • Low Vitamin D/ chronic kidney disease

Management

  • Treat underlying cause - most commonly replacement of vitamin d (e.g. colecalciferol or ergocalciferol). Combined products (AdcalD3 - Vit D + calcium) can also be used (e.g. if poor dietary intake). 

      

Osteopetrosis (Marble bone disease)

Pathology

  • Osteoclast dysfunction results in abnormal bone resorption
  • Results in thick, dense ‘marble’ bones which are easily fractured

Investigations

  • Calcium/phosphate/PTH/ALP levels are usually normal


      

Osteitis Fibrosa Cystica

Pathology

  • Bone disease occurring as a result of advanced primary or secondary hyperparathyroidism

Investigations

  • Bloods
    • High: PTH, Calcium, ALP
    • Low: Phosphate 
  • Imaging
    • Osteopenia, bowing, brown tumours and bone cysts. 

    

Osteogenesis Imperfecta

Pathology

  • An autosomal dominant disease characterised by low levels of type 1 collagen - ‘brittle bone disease’

Clinical Features

  • History of childhood fractures, deafness, teeth abnormalities