Metabolic bone disease Flashcards
Discuss your approach to metabolic bone disease causes
D/o of mineralisation - vitamin D deficiency D/o of matrix formation - osteogenesis imperfecta D/o of excessive/reduced bone absorption - hyperparathyroidism - osteopetrosis
What is the most common cause of rickets in infants?
Vitamin D deficiency
What is the most common cause of rickets in older children?
Dietary calcium deficiency
Inherited hypophosphataemia
What abnormalities can occur with the metabolism of vitamin D?
- Nutritional
- Impaired absorption
- Impaired hydroxylation
- Incr metabolism
- Decr renal synthesis
- End organ resistance
Which substances cause poor calcium bioavailability?
Phytates
Oxalates
Name risk factors for vitamin D deficiency
Lack of sunlight exposure Incr skin pigementation Prolonged breastfeeding Prem Mother vitamin D deficient Vegetarian diet
Name causes of impaired vitamin D absoprtion
Steatorrhoea
Biliary obstruction
Neonatal hepatitis
Name causes of impaired vitamin D hydroxylation
Immature liver
Prem
Severe liver disease
Name causes of increased vitamin D metabolism
Phenobarbitone
Name causes of decreased renal synthesis of 1,25 dihydroxyvitamin D
Renal failure
What abnormalities can occur with the metabolism of phosphate?
- Nutritional
- Impaired absorption
- Renal loss
Name causes of impaired phosphate intake
Prem (soya bean prep)
VLBW (BF not enough)
Name causes of impaired intestinal phosphate absorption
Aluminum hydroxide
Name causes of impaired renal loss of phosphate
- Hypophosphataemia
- Fanconi syndrome
- Distal tubular acidosis
- Tumour induced
What genetic forms are there of hypophosphataemic rickets?
X linked
AD
AR
Which gene is involved in X linked hypophosphataemic rickets
PHEX (inactivation)
Which gene is involved in autosomal dominant hypophosphataemic rickets
FGF23 (activation)
Which gene is involved in autosomal recessive hypophosphataemic rickets
DMP1 (inactivation)
ENPP1 (inactivation)
What is Fanconi syndrome?
A syndrome of inadequate reabsorption in the proximal renal tubules of the kidney
Name causes of Fanconi syndrome
Cystinosis Lowe's syndrome Tyrosinaemia Galactosaemia Hereditary fructose intolerance Wilson's disease Heavy metal toxicity Idiopathic
What do you need to consider in a child with FTT, acidosis and rickets?
Distal tubular acidosis
Name clinical features of metabolic bone disease
Bony deformity Short stature Developmental delay Hypotonia Proximal mm weakness Convulsions Metabolic acidosis Recurrent LRTIs
Name bony deformities
Widening of long bone metaphysis Bow legs Genu varum Harrison's sulcus Rickety rosary Craniotabes Frontal/parietal bossing Kyphoscoliosis
Name radiological features of rickets
Delayed epiphyseal development Growth plate widening Splaying + cupping of metaphysis Irregularity and fraying of metaphysis end Osteopenic bones Thin cortices Trabecular patterns Subperiosteal erosions
