Vitamin D deficiency rickets
Vitamin D deficiency rickets is defective mineralization of the growing cartilaginous growth plate from inadequate vitamin D, most often in a breastfed infant without supplementation, presenting with bowing of the legs, a rachitic rosary, and delayed motor development around 15 months of age. Diagnosis rests on a low 25-hydroxyvitamin D with elevated parathyroid hormone and characteristic metaphyseal cupping and fraying on long-bone radiographs, and first-line treatment is ergocalciferol 2,000 IU PO once daily for 6 weeks with calcium supplementation.
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What this article covers
- Overview
A disease of the growing skeleton: rickets is defective mineralization of the cartilaginous growth plate in children, the pediatric counterpart of osteomalacia (defective mineralization of already-formed bone matrix in adults).
- Epidemiology
Peak presentation in toddlers: the average age at diagnosis is 15 months, coinciding with rapid bone growth and the period when breastfed infants without supplementation have depleted maternal vitamin D stores.
- Risk factors
Exclusive or predominant breastfeeding without vitamin D supplementation: the single most common risk factor, since breast milk vitamin D content is inadequate for infant requirements.
- Pathophysiology
Vitamin D deficiency reduces intestinal calcium absorption: without adequate 1,25-dihydroxyvitamin D, active intestinal calcium transport falls, lowering serum calcium.
- Clinical features
Bowing of the legs (genu varum) is the hallmark finding, appearing as the child begins weight-bearing and progressing with continued ambulation on an inadequately mineralized skeleton.
- Differential diagnosis
X-linked hypophosphatemic rickets: bowing and bone pain similar to nutritional rickets, but 25-hydroxyvitamin D and calcium are normal, phosphorus is low from primary renal wasting, unlike the low…
- Diagnosis
The diagnosis is established by the combination of a low serum 25-hydroxyvitamin D with the secondary biochemical cascade it produces (elevated PTH, low or low-normal calcium, low phosphorus…
- Management
First, replete vitamin D for a 6-week course, dosed by age: infants under 1 year: ergocalciferol 2,000 IU PO once daily children 1-18 years: ergocalciferol 2,000-6,000 IU PO once daily, or 50,000 IU…
- Complications
Hypocalcemic seizures and tetany: can occur at presentation or during illness-associated increased calcium demand before treatment is established, particularly in young infants.
- Prognosis
Excellent with prompt treatment: biochemical abnormalities typically normalize within weeks of starting vitamin D and calcium repletion, and mild to moderate bony deformity often improves…
- Prevention
Supplement all breastfed infants with cholecalciferol 400 IU PO once daily, started shortly after birth and continued throughout breastfeeding until the infant is weaned to at least 32 oz/day of vitamin D-fortified formula or milk.
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Related articles
- Hypocalcemia
Hypocalcemia is a low serum calcium concentration, most often from insufficient parathyroid hormone action (postsurgical or autoimmune hypoparathyroidism, hypomagnesemia, or PTH resistance) or from vitamin D deficiency and chronic kidney disease. Severe or symptomatic disease requires urgent intravenous calcium, while chronic disease is managed with oral calcium, vitamin D repletion, and calcitriol when PTH is absent or the kidney cannot activate vitamin D.
- X-linked hypophosphatemia
X-linked hypophosphatemia is an inherited disorder of excess FGF23 activity that causes renal phosphate wasting at the proximal tubule, producing rachitic bone disease in children and osteomalacia in adults despite normal serum calcium and vitamin D. First-line treatment is oral phosphate salts with calcitriol, or burosumab, an anti-FGF23 monoclonal antibody, given alone and never combined with oral phosphate or active vitamin D.