Rickets

Defective mineralization of the growth plates (in children) leading to soft, deformed bones; most often caused by severe vitamin D deficiency.

• Remains a preventable cause of childhood disability worldwide. Early treatment of rickets prevents lifelong bone deformities and developmental delays, and vitamin D deficiency is a common exam topic.

• Typically seen in infants 6–18 months old with risk factors (e.g., dark skin, exclusive breastfeeding without vitamin D supplements, minimal sun exposure). Early signs are poor growth, delayed sitting or crawling, and irritability.
• Classic skeletal manifestations: craniotabes (soft skull bones), frontal bossing of the forehead, enlarged costochondral junctions (rachitic rosary), widening of wrists and ankles, and bowing of legs (genu varum) once the child starts walking.
• Genetic or renal forms present similarly but often later in childhood. X-linked hypophosphatemic rickets (vitamin D–resistant) may show dental problems (late tooth eruption, enamel defects, recurrent abscesses) and leg bowing despite normal vitamin D intake. Rickets from renal osteodystrophy occurs in children with chronic kidney disease (secondary hyperparathyroidism).

1. Evaluate nutritional history and risk factors (diet, sun exposure, malabsorptive disorders like celiac, or medications like anticonvulsants).
2. Order labs: 25(OH)D level (for vitamin D status), calcium, phosphate, alkaline phosphatase (ALP), and PTH. Nutritional rickets typically shows low 25(OH)D, low Ca and phosphate, high PTH, and very high ALP (reflecting increased osteoblast activity).
3. Obtain X-rays of affected bones (usually wrist or knee): findings include widened growth plates with metaphyseal cupping and fraying, and generalized osteopenia.
4. If vitamin D levels are normal or rickets is refractory to treatment, investigate other causes: check for isolated hypophosphatemia (suggesting phosphate-wasting rickets like XLH) or signs of renal disease (uremia, high creatinine) indicating renal rickets. Consider genetic testing or referral to a specialist for atypical cases.

1. For nutritional rickets: replete vitamin D stores (e.g., high-dose ergocalciferol/cholecalciferol for 6–12 weeks, then maintenance 400–600 IU daily) and ensure adequate dietary calcium and sun exposure.
2. Hereditary or refractory rickets often requires calcitriol (active vitamin D) and phosphate supplementation. For example, X-linked hypophosphatemic rickets is treated with oral phosphate plus calcitriol; severe cases may benefit from burosumab (monoclonal antibody against FGF23). Rickets due to CKD (renal osteodystrophy) is managed with calcitriol and phosphate binders alongside treating the kidney disease.
3. Monitor response with labs and X-rays (healing of rickets takes months). In severe cases, bracing or orthopedic surgery may be needed to correct residual bone deformities after medical therapy.

• Breast milk contains very little vitamin D—so exclusively breastfed infants need vitamin D supplementation (400 IU daily) to prevent rickets.
• Nutritional (calcipenic) rickets: low Ca → high PTH (secondary hyperparathyroidism) → phosphate wasting (low phosphate). In contrast, X-linked hypophosphatemic rickets involves isolated renal phosphate loss (normal Ca, low phosphate).
• Radiologic buzzwords: rachitic rosary (beaded ribs) on exam, and metaphyseal cupping & fraying on X-ray are classic for rickets.

• Severe hypocalcemia from rickets can cause tetany or seizures (e.g., infant with convulsions) – requires urgent IV calcium and vitamin D therapy.
• Profound vitamin D deficiency may lead to dilated cardiomyopathy and heart failure in infants (rare). Any signs of cardiopulmonary distress in rickets warrant hospitalization and aggressive management.

1. Child with bow legs or other bony deformities + risk factors (poor diet, low sun) → suspect rickets.
2. Confirm rickets: check labs (25-OH vitamin D, Ca, phosphate, ALP, PTH) and obtain wrist or knee X-ray.
3. If vitamin D is low (with low Ca/P, high PTH) → nutritional rickets confirmed: start vitamin D supplementation and calcium.
4. If vitamin D is normal but phosphate is low (± normal Ca) → consider phosphate-wasting rickets (e.g., XLH); refer for genetic evaluation and treat with phosphate + calcitriol.
5. If rickets occurs in a child with CKD or malabsorption → address the underlying disease (optimize nutrition or renal care) and treat with active vitamin D + appropriate dietary support.

• Dark-skinned 1-year-old, exclusively breastfed without vitamin D, with delayed walking, prominent forehead, and bow legs → nutritional rickets (vitamin D deficiency).
• School-age child with short stature, leg bowing, and recurrent dental abscesses despite good oral care → X-linked hypophosphatemic rickets (familial phosphate-wasting).
• Child with end-stage renal disease (on dialysis) who has bone pain, growth failure, and X-ray showing rachitic changes → renal osteodystrophy (rickets from CKD).