Rickets

Question 1

What is rickets?

Answer 1

Defective bone mineralisation causing ‘soft’ and deformed bones.

Same as osteomalacia in adults.

Question 2

What are the causes of rickets?

Answer 2

Deficiency in vitamin D or calcium.

Question 3

What are the risk factors for rickets?

Answer 3

Darker skin, low exposure to sunlight, colder climates, a lot of time indoors, prolonged breastfeeding.

Question 4

What is a rare form of rickets called?

Answer 4

Hereditary hypophosphataemic rickets is a rare form caused by genetic defects that result in low phosphate in the blood.

The most common form is x-linked dominant, but it also has other modes of inheritance.

Question 5

What is the pathophysiology of rickets?

Answer 5

• vitamin D is a hormone created from cholesterol by the skin in response to UV radiation
• reduced sun exposure without vitamin D supplementation leads to vitamin D deficiency
• patients with malabsorption disorders (eg. IBD), are more likely to have vitamin D deficiency
• they kidneys are essential in metabolising vitamin D to its active form, therefore vitamin D deficiency is common in CKD
• vitamin D is essential in calcium and phosphate absorption from the intestines and kidneys
• vitamin D is also responsible for regulating bone turnover and promoting bone reabsorption to boost the serum calcium level
• inadequate vitamin D leads to a lack of calcium and phosphate in the blood
• as calcium and phosphate are required for the construction of bone, low levels result in defective bone mineralisation
• low calcium causes a secondary hyperparathyroidism as the parathyroid gland tries to raise the calcium level by secreting parathyroid hormone
• PTH stimulates increased reabsorption of calcium from the bones
• this causes further problems with bone mineralisation

Question 6

What are the presentations of rickets?

Answer 6

• vitamin D and rickets patients may not have any symptoms
• lethargy
• bone pain
• swollen wrists
• bone deformity
• poor growth
• dental problems
• muscle weakness
• pathological or abnormal fractures

Question 7

What bone deformities can occur in rickets?

Answer 7

• bowing of the legs, where the legs curve outwards
• knock knees, where the legs curve inwards
• rachitic rosary, where the end of the ribs expand at the costochondral junctions causing lumps along the chest
• craniotabes, which is a soft skull, with delayed closure of the sutures and frontal bossing
• delayed teething with under development of the enamel

Question 8

What investigations are needed for rickets?

Answer 8

• serum 25-hydroxyvitamin D is the lab investigation for vitamin D → less that 25nmol/L established a diagnosis of vitamin D deficiency ⇒ rickets
• x-ray needed to diagnose rickets → it may also show osteopenia (more radiolucent bones)
• serum calcium may be low
• serum phosphate may be low
• serum alkaline phosphatase may be high
• PTH may be high

Question 9

What additional investigations should be done to look for other pathologies?

Answer 9

• FBC and ferritin for iron deficiency anaemia
• inflammatory markers eg. ESR and CRP for inflammatory conditions
• kidney function tests for kidney disease
• LFTs for liver pathology
• malabsorption screen eg. anti-TTG antibodies for coeliac disease
• autoimmune and rheumatoid tests for inflammatory autoimmune conditions

Question 10

What should breastfeeding women take?

Answer 10

• breastfed babies are at a higher risk of vitamin D deficiency compared with formula fed babies, as formula feed is fortified with vitamin D
• breastfeeding women and all children should take a vitamin D supplement → supplements containing 400 IU (10 micrograms) per day for children and young people

Question 11

How can children with vitamin D deficiency be treated?

Answer 11

• with vitamin D (ergocalciferol)
• the doses for treatment of vitamin D deficiency depend on the age
• the dose for children between 6 months and 12 years is 6000 IU per day for 8-12 weeks
• children with features of rickets should be referred to a paediatrician
• vitamin D and calcium supplementation is used to treat rickets