Define Rickets. Describe its causes, clinical features, investigations and management.

Definition

Rickets is a disorder of the growing skeleton in which there is defective mineralisation of the growth plate (physis) and of newly formed osteoid, most often due to vitamin D deficiency. Because it affects the physis, rickets causes the characteristic bony deformities of childhood; the adult equivalent (after physeal closure) is osteomalacia.

Causes

The commonest cause is vitamin D deficiency — from inadequate sunlight exposure, poor dietary intake, or malabsorption. Other causes include renal disease (renal rickets / renal osteodystrophy), hypophosphataemic (vitamin-D-resistant) rickets (an X-linked renal phosphate-wasting disorder), and defects of vitamin D metabolism. Nutritional deficiency of calcium also contributes.

Clinical signs of rickets result from soft, poorly mineralised bone deforming under load and from swelling at the growth plates.

Clinical Features

The soft, under-mineralised bones deform and the growth plates widen. Features include bow legs (genu varum) or knock knees, swelling at the wrists and ankles, the ‘rickety rosary’ (beading at the costochondral junctions), Harrison’s sulcus, frontal bossing and delayed closure of the fontanelles, delayed dentition, short stature and hypotonia. Hypocalcaemia may cause tetany or seizures in severe cases.

Investigations

Biochemistry: low or low-normal calcium, low phosphate, markedly raised alkaline phosphatase, low 25-hydroxyvitamin D, and a raised PTH (secondary hyperparathyroidism). Radiographs show characteristic changes at the metaphyses of rapidly growing bones (wrist, knee): widening, cupping, splaying and fraying of the metaphysis, with a widened growth plate and osteopenia.

Management

The mainstay is correction of the deficiency: vitamin D (as cholecalciferol/ergocalciferol, in treatment then maintenance doses) together with adequate calcium, and treatment of any underlying cause (e.g. Phosphate supplements and active vitamin D analogues for hypophosphataemic rickets; management of renal disease). With biochemical and radiological monitoring, mild deformities often correct with growth; residual or severe deformity may need guided growth or corrective osteotomy once the metabolic disease is controlled.

• Defective mineralisation of the growing skeleton (physis); usually vitamin D deficiency.
• Signs: bow legs/knock knees, rickety rosary, wide wrists, Harrison’s sulcus, frontal bossing.
• Biochemistry: ↓Ca, ↓PO₄, ↑ALP, ↓vitamin D, ↑PTH.
• X-ray: cupping, splaying, fraying of the metaphysis; widened physis.
• Vitamin D + calcium (treat the cause); correct residual deformity surgically once biochemically controlled.