{
 "topic": "Vitamin D Deficiency",
 "slug": "vitamin-d-deficiency",
 "category_id": 15039,
 "summary": "Low 25-hydroxyvitamin D from limited sun exposure or intake, its risk groups, laboratory findings, and the vitamin D doses used for prevention and treatment in infants and children.",
 "written_by": "claude-sonnet",
 "references": [
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  {
   "title": "Pediatric Decision-Making Strategies",
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  {
   "title": "Netters Pediatrics (Florin \u0422., Ludwig St.)",
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   ]
  }
 ],
 "short": [
  {
   "title": "In short",
   "content": "- Vitamin D status is assessed by serum 25-hydroxyvitamin D (25OHD/calcidiol): insufficiency is 15-20 ng/mL and deficiency is under 15 ng/mL by one definition; another source uses 25-OH-D \u226415 ng/mL for deficiency and >20 ng/mL as sufficient for healthy US children.\n- Vitamin D is produced in skin from 7-dehydrocholesterol via UVB, or consumed as D3 (meat, fish) or D2 (supplements), then converted in the liver to 25-hydroxyvitamin D and in the kidney to the active form, 1,25-dihydroxyvitamin D (calcitriol).\n- Breast milk is a poor source of vitamin D, so exclusively breastfed infants without supplementation are a major at-risk group, along with dark-skinned children, premature infants, and children with fat malabsorption (cholestatic liver disease, cystic fibrosis, Crohn disease/IBD).\n- Other risk factors: limited sun exposure (sunscreen use, conservative clothing, winter season, high latitude), anticonvulsants that induce hepatic P450 enzymes, vegan diets using unfortified soy or rice milk, and, more recently recognized, obesity.\n- Vitamin D deficiency is common in pediatric IBD (prevalence up to 35%), linked to reduced intake, less sun exposure, and malabsorption from intestinal inflammation; risk factors there include winter season, darker skin, and upper GI tract involvement.\n- Primary consequences are on calcium metabolism: hypocalcemia, hypophosphatemia, tetany, osteomalacia, and rickets; in very young infants, deficiency is more likely to present as hypocalcemia (with possible seizures) than as overt rickets.\n- Classic laboratory pattern: low phosphorus, high alkaline phosphatase, high PTH, low 25(OH)D, and low-to-high 1,25-dihydroxyvitamin D, with low-normal or low total calcium and normal bicarbonate.\n- Prevention: the American Academy of Pediatrics (2008) recommends 400 IU/day of vitamin D for all infants from birth (breastfed infants supplemented until taking 1 quart of formula daily), and 600 IU/day for healthy children 1-18 years old (some sources describe 600 IU/day specifically for older children with risk factors for inadequate intake).\n- Prognosis is generally excellent with treatment \u2014 radiologic and laboratory normalization within a few months \u2014 though severe or prolonged deficiency can leave permanent bony deformity, short stature, or (rarely) fatal prolonged laryngospasm."
  }
 ],
 "long": [
  {
   "title": "Definition",
   "content": "Vitamin D status is screened in at-risk infants and children by measuring serum 25-hydroxyvitamin D (25OHD, also called calcidiol). Vitamin D insufficiency is defined as a level between 15 and 20 ng/mL, and vitamin D deficiency as a level below 15 ng/mL. A separate reference notes that serum 25-OH-D concentrations above 20 ng/mL are considered sufficient for healthy children in the United States, a cutoff set mainly to prevent rickets in early childhood, while levels at or below 15 ng/mL define deficiency. The broader physiologic goal is a serum 25-hydroxyvitamin D level above 50 nmol/L (about 30 ng/dL)."
  },
  {
   "title": "Pathophysiology",
   "content": "Vitamin D is synthesized in skin from 7-dehydrocholesterol under UVB exposure as cholecalciferol (vitamin D3), or obtained from food as D3 (meat, fish) or D2 (supplements). It is then hydroxylated in the liver to 25-hydroxyvitamin D and further hydroxylated in the kidney to 1,25-dihydroxyvitamin D (calcitriol), the physiologically active form that governs calcium and phosphate regulation and bone mineralization. Vitamin D also has an expanding recognized role in immune regulation. Transplacental transport of maternal 25-D typically supplies an infant's needs for the first one to two months of life unless the mother is severely vitamin D deficient; after that, formula-fed infants receive adequate vitamin D from formula, while breastfed infants \u2014 because breast milk has a low vitamin D content \u2014 depend on cutaneous synthesis or supplementation."
  },
  {
   "title": "Etiology",
   "content": "Deficiency results from a lack of UVB exposure, inadequate dietary intake, fat malabsorption, or liver or kidney disease impairing conversion to active metabolites, and rarely from genetic disorders. It occurs most frequently in infancy from a combination of poor intake and inadequate cutaneous synthesis. Risk factors include exclusive or protracted breastfeeding without supplementation, dark skin pigmentation (increased melanin reduces cutaneous vitamin D synthesis), marked prematurity, use of sunscreens or conservative clothing, winter season and higher latitude, anticonvulsant medications that induce hepatic P450 enzymes, fat malabsorption syndromes (cholestatic liver disease, cystic fibrosis, Crohn disease/inflammatory bowel disease), impaired biliary secretion, and vegan diets using unfortified soy or rice milk. Children with restrictive diets (e.g., for autism) or elimination diets (e.g., for feared allergies) are also at risk. Obesity has more recently been recognized as a risk factor. Decreased maternal vitamin D status can compound infant risk both by lowering breast milk vitamin D content and by reducing transplacental delivery. In pediatric IBD specifically, deficiency (25-OH-D \u226415 ng/mL) has a prevalence as high as 35%, related to reduced intake, decreased sun exposure, and malabsorption from intestinal inflammation, with winter season, darker skin, and upper gastrointestinal involvement as consistent risk factors."
  },
  {
   "title": "Clinical features",
   "content": "Manifestations center on disrupted calcium metabolism: hypocalcemia, hypophosphatemia, tetany, osteomalacia, and rickets are the most common clinical features. At very young ages, vitamin D deficiency is more likely to present as hypocalcemia \u2014 including hypocalcemic seizures \u2014 than as overt rickets. Additional features include muscular hypotonia, craniotabes, growth failure, lethargy, irritability, myopathy, dysarthria, impaired immune response, and increased susceptibility to respiratory infection and pneumonia; muscle weakness can delay motor development. Mild to moderate deficiency may be present for months before rickets is clinically obvious. Prolonged laryngospasm from severe hypocalcemia is occasionally fatal."
  },
  {
   "title": "Diagnostics",
   "content": "The classic biochemical pattern of vitamin D-deficient rickets is low-normal or low total calcium, low phosphate, high alkaline phosphatase, high parathyroid hormone (secondary hyperparathyroidism), low 25-hydroxyvitamin D, variable (low-to-high) 1,25-dihydroxyvitamin D, and normal bicarbonate. Screening with serum 25-hydroxyvitamin D is recommended for infants and children with risk factors, including all children with darker skin and those who do not consume fortified dairy products."
  },
  {
   "title": "Treatment",
   "content": "Treatment includes vitamin D supplementation together with calcium and phosphorus supplements and foods rich in these nutrients. Most children with nutritional vitamin D deficiency respond excellently to treatment, with radiologic healing within a few months and rapid normalization of laboratory values."
  },
  {
   "title": "Prevention",
   "content": "Most nutritional rickets can be prevented by universal vitamin D administration: the American Academy of Pediatrics (2008) recommends 400 IU/day for all infants from birth, continued in breastfed infants until they are consuming 1 quart of formula daily. Older children and adolescents who do not obtain 400 IU/day through diet should take a 400 IU vitamin D supplement, and the RDA for healthy children 1-18 years old is 600 IU/day; children with risk factors for inadequate intake should receive 600 IU/day. Vitamin D can be given as part of a multivitamin or as a standalone supplement."
  },
  {
   "title": "Complications",
   "content": "Many bony malformations of vitamin D-deficient rickets improve dramatically with treatment, but children with severe disease can be left with permanent skeletal deformity and short stature; orthopedic intervention for leg deformity is rarely needed and generally deferred until the metabolic bone disease has healed and the deformity is both unlikely to self-resolve and functionally significant. Increased risk of pneumonia and delayed motor development from muscle weakness are recognized complications, and prolonged laryngospasm from severe hypocalcemia is occasionally fatal."
  }
 ],
 "clinical": [
  {
   "title": "Recognition and workup at the bedside",
   "content": "Consider vitamin D deficiency in an infant or child with hypocalcemic symptoms (tetany, seizures), growth failure, lethargy, irritability, hypotonia, craniotabes, or recurrent respiratory infection, particularly in an exclusively breastfed infant without supplementation, a child with dark skin pigmentation, prematurity, fat malabsorption (cholestatic liver disease, cystic fibrosis, IBD), anticonvulsant use, or a vegan diet using unfortified soy or rice milk. Screen with serum 25-hydroxyvitamin D: a level under 15 ng/mL defines deficiency and 15-20 ng/mL defines insufficiency. Expect the classic pattern of low-normal or low calcium, low phosphate, high alkaline phosphatase, and high PTH in vitamin D-deficient rickets; in very young infants, hypocalcemia (including seizures) may be the presenting feature rather than overt rickets."
  },
  {
   "title": "Supplementation and treatment doses",
   "content": "For prevention, give all infants 400 IU/day of vitamin D from birth; continue supplementation in breastfed infants until they are taking 1 quart of formula daily. Older children and adolescents not obtaining 400 IU/day through diet should take a 400 IU vitamin D supplement, and the RDA for healthy children 1-18 years is 600 IU/day, which is also the dose recommended for older children with risk factors for inadequate intake. Once deficiency or rickets is diagnosed, treatment combines vitamin D with calcium and phosphorus supplementation and dietary sources rich in these nutrients; most children respond well, with radiologic healing within a few months and rapid normalization of laboratory values."
  }
 ]
}