Rickets

Rickets is a failure in the mineralization of growing bone. It is most commonly secondary to nutritional causes. In fully developed bone this is called Osteomalacia. The daily vitamin D requirements are 400 IU.

CAUSES

Vitamin D intake inadequate: 

1. Nutritional: Prematurity (osteopenia of prematurity), Breast-fed infants more at risk, Poorly fed infants (malnutrition).
2. Malabsorption- coeliac disease, steatorrhoea, cystic fibrosis, Inadequate sunlight exposure (especially in dark-skinned).                                                        

Metabolism of vitamin D:

• Renal disease.NB: PO4 Increases
• Liver disease
• Anticonvulsants, e.g.phenytoin (metabolizes vitamin D)

Phosphate excretion increased:

• Familial hypophosphatemic rickets
• Vitamin D-dependent rickets - type I or type II (receptor defect)
• Fanconi syndrome

CLINICAL FEATURES

1. Head - large anterior fontanelle with delayed closure (>2 years), craniotabes (ping-pong ball skull), frontal bossing.

   

   Ping-pong ball skull

   
   
2. Chest - enlargement of costochondral junctions (Rachitic or rib rosary), Harrison sulcus, pigeon chest.
3. Thickened wrists and ankles.
4. Bowlegs, knock knees.
5. Dwarfism, pot belly, muscular weakness, kyphosis, small pelvis, coxa vara.
6. Late dentition with enamel defects.
7. Greenstick fractures.

INVESTIGATIONS

• Biochemical investigations.
• X-ray of the left wrist (or left knee if <2 years):
• Widened epiphyseal plate
• Cupping and fraying of the metaphysis
• Increased joint space
• Line of calcifications seen when healing
• Cysts, subperiosteal erosions, fractures, Looser's zones, osteopenia if severe.

TREATMENT

This is with vitamin D in the necessary form:

1. Nutritional rickets - Calciferol (D3)
2. Renal disease - Alphacalcidol (1 alpha OHD3) or calcitriol (1,25(OH)2D3)