27th February 2025

Rickets and osteomalacia

Severe vitamin D deficiency (through decreased sun exposure, poor diet or malabsorption) is the most common cause of rickets, seen in children before growth plate closure, and osteomalacia.

Rickets

Rickets is characterised by inappropriate expansion of the growth plate, preventing its replacement by osteoblasts.

Clinical features include developmental delay, hypotonia, bowing of the legs, end thickening of long bones, ‘rickety rosary’ (costochondral nodularity), craniotabes, and frontal/parietal bossing.

Osteomalacia

Osteomalacia is characterised by impaired mineralisation of bone matrix proteins, with hypocalcaemia and hypophosphataemia directly involved in the pathophysiology. Prolonged deficiencies in these minerals for any reason may, therefore, result in osteomalacia.

Clinical manifestations include fatigue, generalised aches and pains, bone pain and tenderness, proximal myopathy with waddling gait, and an increased risk of fractures. If not already present, significant hypocalcaemia can eventually develop, as osteoclasts are unable to further mobilise calcium from unmineralised bone. High bone turnover often results in a raised ALP.

Though definitive, bone biopsy is rarely performed, and instead, diagnosis most often relies on history, examination and biochemistry. Imaging may also be of use as plain film radiographs might show transverse lines of increased lucency (pseudofractures or Looser’s zones), and DXA may demonstrate low BMD. Alongside the increased risk of fracture, low BMD often means osteomalacia is mistaken for osteoporosis. However, in contrast to osteomalacia, the ratio of mineralised to unmineralised bone remains constant in osteoporosis.

Treatment consists of loading doses of vitamin D followed by daily maintenance therapy, with calcium supplementation as required.