RICKETS ( children )

OSTEOMALACIA ( adults )

lack of vitamin D:

fat malabsorption

disorders of vitamin D metabolism [low Ca causes 2� hyperPTH and renal P loss]:

renal osteodystrophy [uraemic bone disease; chronic renal disease causing phosphate retention, vitamin D resistance, impaired 1a -hydroxylation of vitamin D, secondary hyperparathyroidism and severe hypocalcaemia]

liver disease (impaired 25-hydroxylation of vitamin D)

vitamin D-dependent rickets [autosomal recessive 1a-OHase deficiency]

drugs causing increased inactivation of vitamin D:

phenobarbitone / primidone

other enzyme inducers

renal phosphate loss:

familial hypophosphataemia [vitamin D-resistant rickets; sex-linked dominant]

renal tubular rickets (tubular disorders with phosphate loss):

cystinosis

phosphate depletion:

long term use of aluminium-containing antacids

1� mineralisation defects:

etidronate treatment