Osteomalacia

Vitamin D deficiency can lead to osteomalacia (rickets) in children. This may present with proximal muscle weakness, musculoskeletal pain and general irritability, and affected children are often described as miserable or fatigued.

Classical features of rickets include bowing of the legs and apparent joint swelling, reflecting underlying abnormalities of bone mineralisation.

Causes are varied and include dietary deficiency, inadequate sun exposure, malabsorption (for example coeliac disease or inflammatory bowel disease), renal disease, and certain medications such as antiepileptic drugs. There are also inherited forms of rickets.

Investigation

Diagnosis is supported by a combination of clinical features and investigations. Blood tests typically include bone profile (calcium, phosphate, alkaline phosphatase), parathyroid hormone and 25-hydroxyvitamin D levels. Radiographs may demonstrate classical changes such as widening and cupping of the metaphyses.

The threshold for defining vitamin D deficiency in asymptomatic children remains controversial, and results should be interpreted in the clinical context.