Rickets (Complete) Flashcards
Define rickets
Skeletal disorder caused by deficiency of vitamin D, calcium or phosphate.
Results in formation of soft bone due to failed mineralisation of bone matrix
What are the main risk factors for rickets?
Lack of sunlight
Dietary deficiency of calcium (developing countries)
Prolonged breastfeeding without vitamin D supplementation
Unfortified cow’s milk/formula
Malabsorption disorders (e.g. CF, coeliac disease)
Why is breastfeeding associated with rickets?
Breast milk has low amounts of vitamin D
Hence infants exclusively breastfed without any fortification at higher risk
Give 2 examples of malabsorption disorders associated with vitamin D deficiency
CF
Coeliac disease
What are the main clinical features of rickets?
Bone and joint pain
Stunted growth
Dental deformities
Ricket rosary (costochrondral joint swelling)
Skeletal abnormalities
- Pigeon chest
- Spinal curvature (kyphoscoliosis)
Lower limb abnormalities
- Infants: genu varum (bow legs)
- Older children: genu valgum (knock knees)
Proximal muscle weakness
Ricket rosary (costochondral joint swelling)
Pigeon chest
Which lower limb deformity is more likely to occur in toddlers versus older children?
Genu varum (bow leg)
Which lower limb deformity is more likely to occur in older children versus toddlers
Genu valgum
What aditional presentations are indicative of a severe case of rickets?
Bone fragility and fractures
Hypocalcaemia
* Irritability
* Seizures
* Intellectual disability
* Tetany
* Laryngospasms (apnoea and stridor)
Dilated cardiomyopathy
What are the main investigations to consider for patients with suspected rickets?
Bedside:
Urinalysis
Bloods:
25-hydroxyvitamin D levels (calcidiol): Low
Serum calcium
Serum phosphate
Serum PTH
LFT
U&E: Check for underlying kidney problem resulting in vit D deficiency
Imaging:
X-ray
What urinalysis/lab findings are suggestive of hypocalcaemic rickets?
Urinalysis:
- Decreased urinary calcium
- Increased urinary phosphorus
Bloods:
Low serum calcium (<2.3 mmol/L)
Low phosphate (in some cases)
High PTH
Low 25-hydroxyvitamin D (<25 nmoll/L)
Raised ALP (alkaline phosphatase)
Why does ALP levels rise in hypocalcaemic rickets?
ALP can be produced by osteoblasts and plays a role in bone mineralisation
Due to failure of mineralisation in rickets, osteoblasts increase ALP production to compensate
What investigation findings are suggestive of hypophosphataemic rickets?
Urinalysis:
Urinary calcium: Normal
Urinary phosphorus: High
Bloods:
Normal serum calcium
Low serum phosphorus
High ALP
Normal 25-hydroxyvitamin D
Normal PTH
What radiological findings are indicative of rickets?
Widening of epiphyseal plates
Cupping
Fraying
Looser’s zone (Pseduofractures)
Looser’s zone
N.B. Pseudofractures associated with osteomalacia/rickets
What histological findings are seen in patients with rickets?
Osteoids (excess of unmineralised bone)
How are patients with rickets managed?
Conservative:
Diet + Lifestyle modifications: High calcium/vit D/phosphate diet + sunlight exposure
Medicine:
Vitamin D supplements
Calcium supplements
Phosphate supplements
Surgical:
Orthapaedic surgery for severe cases
What differentials should be considered alongside rickets?
Osteomalacia
Hypophosphatasia
Hereditary hypophosphataemic rickets
Osteogenesis imperfecta
How does osteomalacia differ to rickets?
Presents with bone pain and lab findings similar to rickets however:
More common in adults
Associated with pathologic fractures versus bone deformities
How does hypophosphatasia differ to rickets?
Genetic autosomal recessive condition affecting gene encoding ALP
More prominent dental abnormalities (premature loss of primary teeth)
Associated with short-stature, fragile bones and craniosynostosis (premature fusion of skull bones)
Low ALP versus high ALP in rickets
How does hereditary hypophosphataemic rickets differ to rickets?
An X-linked inheritable form of rickets due to altered FGF23 levels
Results in phosphate wasting in kidneys
Low phosphate in context of normal vitamin D
Presents identical to typical rickets but is refractory to vitamin D supplementation
Suspect this in cases of refractory cases of rickets
How does osteogenesis imperfecta rickets differ to rickets?
Presents with bone fracture and fragility
Blue sclera
Hearing loss
Normal labs
