Vitamin D deficiency results in myopathy (proximal weakness) and musculoskeletal aches and pains and children are often miserable.
Rickets can result in classical signs of bow legs and swollen joints. The causes may be due to malabsorption (e.g coeliac disease, inflammatory bowel disease), dietary deficiency, inadequate sun exposure, renal disease and drugs (e.g. antiepileptic drugs). There are also inherited forms.
Investigations include blood tests (bone chemistry, parathyroid hormone and 25 hydroxyvitamin D) and radiographs which may show typical changes (e.g widened metaphyses). The threshold to define vitamin D deficiency in asymptomatic individuals is controversial.