Bone disorder characterized by soft, weak, and deformed bones
Predominantly caused by Vitamin D deficiency or impaired vitamin D metabolism, but can also be due to hypocalcemia
More common in areas with high rates of early childhood malnutrition/starvation
The predominant cause is a Vitamin D deficiency, but also inadequate calcium and impaired metabolism of vitamin D may also lead to<unk> 
Gained from diet, supplements, or sunlight exposure
Fortified foods (mainstay), supplements, fatty fish, egg yolks, fish liver oil, and some mushrooms
Synthesis of vitamin D occurs in the skin through exposure to ultraviolet B radiation from sunlight
Hydroxylated in liver→ 25-hydroxyvitamin D, which is further hydroxylated in kidney or extrarenally→ 1,25-dihydroxyvitamin D (active form)
Second hydroxylation regulated by PTH, serum calcium, and phosphorus levels
Vitamin D acts to:
Stimulate intestinal calcium absorption
Maintain adequate phosphate levels for bone development
Regulate cell growth proliferation and apoptosis
Modulate immune function and inflammation reduction
Fortified foods (mainstay), supplements, fatty fish, egg yolks, fish liver oil, and some mushrooms
Synthesis of vitamin D occurs in the skin through exposure to ultraviolet B radiation from sunlight
Second hydroxylation regulated by PTH, serum calcium, and phosphorus levels
Stimulate intestinal calcium absorption
Maintain adequate phosphate levels for bone development
Regulate cell growth proliferation and apoptosis
Modulate immune function and inflammation reduction
Inadequate intake
Maternal vitamin D deficiency: in utero, 25-hydroxyvitamin D passes through the placenta to the infant
Exclusive breastfed infants without vitamin D supplementation
Inadequate sunlight exposure, dark skin pigmentation
Impaired vitamin D absorption
Crohn's disease, cystic fibrosis
Impairment in conversion of vitamin D into active metabolites
Renal Failure, Liver failure
Maternal vitamin D deficiency: in utero, 25-hydroxyvitamin D passes through the placenta to the infant
Exclusive breastfed infants without vitamin D supplementation
Crohn's disease, cystic fibrosis
Renal Failure, Liver failure
Hereditary<unk> 
Kidneys unable to retain phosphate
Nutritional<unk> 
Vitamin D Resistant<unk> 
Vitamin D Dependant<unk> 
Congenital<unk> 
Kidneys unable to retain phosphate
Rickets
Hypocalcemia
Scurvy
Hyperparathyroidism
Pruritus ani
Hypophosphatemia
Porphyria
Malignancy