Rickets Flashcards
What is rickets?
A condition that results in weak or soft bones in children
What is the most common cause of rickets?
Vitamin D deficiency
Where is vitamin D derived from?
Two main sources;
- Synthesis from skin following exposure to UV light
- Diet
What are the main functions of vitamin D?
- Regulation of calcium and phosphate metabolism
- Functions in the immune system
What is the result of vitamin D being involved in the regulation of calcium and phosphate metabolism?
Makes it essential for bone health
What happens if vitamin D is not supplied in adequate levels in childhood?
Rickets will develop
What does vitamin D deficiency usually result from?
- Inadequate UVB exposure
- Deficient intake
- Defective metabolism of vitamin D
What effect does a vitamin D deficiency have on calcium?
It causes a low serum calcium
What is the result of a low serum calcium?
It triggers the secretion of PTH
What effect does an increased secretion of PTH have?
- Normalises calcium, but demineralises bone
- Causes loss of renal phosphate, and subsequently low serum phosphate levels
What is the result of low serum phosphate levels?
It further reduces the potential for bone calcification
What are the categories of causes of rickets?
- Nutritional (primary) rickets
- Intestinal malabsorption
- Problems with 25-hydroxyvitamin D
- Problems with 1,25-dihydroxyvitamin D
What are the risk factors for primary rickets?
- Living in northern latitudes
- Dark skin
- Decreased exposure to sunlight
- Maternal vitamin D deficiency
- Diets low in calcium, phosphorus, and vitamin D
- Macrobiotic, strict vegan diets
- Prolonged parenteral nutrition in infancy
Give an example of when the diet may be low in calcium, phosphorus, and vitamin D
Exclusive breastfeeding into late infancy
What are the causes of intestinal malabsorption?
- Small bowel enteropathy
- Pancreatic insufficiency
- Cholestatic liver disease
Give an example of a small bowel enteropathy that can lead to rickets
Coeliac disease
Give an example of a cause of pancreatic insufficiency that can lead to rickets
Cystic fibrosis
What are the causes of problems with 25-hydroxyvitamin D?
- Defective production
- Increased metabolism
- Defective production
Give a cause of defective production of 25-hydroxyvitamin D
Chronic liver disease
Give a cause of increased metabolism of 25-hydroxyvitamin D
Enzyme induction by anticonvulsants
What are the causes of defective production of 1,25-dihydroxyvitamin D
- CKD
- Fanconi syndrome
- Inherited disorders
How can rickets present?
- Craniotabes
- Rachitic rosary
- Widened wrists and ankles
- Harrison’s sulcus
- Poor growth/short stature
- Delayed dentition
- Bowing of weight-bearing bones
- Hypotonia
- Seizures
- Cardiomyopathy/heart failure
What are craniotabes?
Softening or thinning of the skull in infants and children, mostly seen in occipital and parietal bones
How do craniotabes present?
The bones are soft, and when pressure is applied they will collapse underneath it
