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- Osteomalacia refers to impaired bone mineralization, caused primarily by deficiencies in vitamin D and/or calcium.
- In children, osteomalacia leads to growth plate abnormalities, termed rickets.
- The prevalence of rickets and osteomalacia is very high in many parts of the world.
- Reported with increasing frequency in the United States since the 1980s
- Vitamin D supplements should be given to breastfed infants and high-risk individuals.
- In the United States and Canada, cow’s milk, infant formula, and cereals are fortified with vitamin D.
Rickets arises due to decreased availability of phosphorus and calcium to mineralize the skeletal matrix, leading to growth plate disorganization and accumulation of undermineralized osteoid. This results in growth plate expansion, bone weakening, and skeletal deformities.
Primary causes include the following:
- Insufficient vitamin D and/or calcium intakes (common)
- Insufficient phosphorus intake (rare)
- Deficient sunlight exposure
- Celiac disease
- Cystic fibrosis
- Liver disease
- Renal tubular defects
- Fanconi syndrome
- Renal tubular acidosis
- Abnormalities in vitamin D metabolism
- Anticonvulsant use
- Liver disease
- Genetic forms (see “Table 1.”)
|Ca||Phos||Alk phos||iPTH||25-(OH)D||1,25-(OH)2D||Urine Ca/ Cr||TRP|
|Nutritional/insufficient sunlight||N or ↓||↓||↑||↑||↓||↑||↓||↑|
|Malabsorption||N or ↓||↓||↑||↑||↓||↑||↓||↑|
|Renal tubular defects||N or ↓||↓||↑||↑||N||↑||↑||N or ↓|
|Altered vitamin D metabolism||N or ↓||↓||↑||↑||↓||↑||↓||↑|
|Genetic forms of rickets|
|X-linked, AD, and AR hypophosphatemic rickets||N||↓||↑||N or ↑||N||N or ↑||N or ↓||↓|
|Vitamin D receptor mutations (Vitamin D resistance)||↓||↓||↑||↑||N||↑||↓||↑|
|Hereditary hypophosphatemic rickets with hypercalciuria||N or ↓||↓||↑||↑||N||↑||↑||↓|
|Hypophosphatasia||N or ↑||N or ↑||↓||N or ↓||N||N or ↓||N or ↑||N|
Ca, calcium; Phos, phosphorus; Alk phos, alkaline phosphatase; iPTH, intact parathyroid hormone; 25-(OH)D, 25-vitamin D; 1,25-(OH)2D, 1,25-dvitamin D; Ca/Cr, calcium/creatinine ratio; TRP, tubular reabsorption of phosphorus ([1– (U phos × P Cr/U Cr × S Phos)] × 100, normal 85–95%); N, normal; AD, autosomal dominant; AR, autosomal recessive
- Infants born to vitamin D–deficient mothers
- Low birth weight and/or prematurity
- Breastfeeding without vitamin D supplementation
- Poor nutrition
- Increased skin pigmentation
- Higher latitudes and winter months
- Use of sunscreens
- Renal tubulopathies