MSK - Rickets Disease

Question 1

Definition

Answer 1

Metabolic bone disorder characterized by defective mineralization of the growth plate cartilage in children, leading to skeletal deformities and growth impairment. Adults experience a similar condition, called osteomalacia .

Question 2

Aetiology

Answer 2

• Nutritional rickets: due to inadequate intake of vitamin D or calcium (MC)
• Hypophosphataemic rickets: due to renal phosphate wasting. This is either an isolated disorder or part of a tubular disorders, such as Fanconi syndrome.
• Calcipaenic rickets: due to abnormal vitamin D metabolism or resistance.

Question 3

Effects of Vit D deficiency

Answer 3

The most common cause is vitamin D deficiency , which results in inadequate calcium and phosphate absorption from the gastrointestinal tract, leading to hypocalcaemia and secondary hyperparathyroidism.

Question 4

Epidemiology and Risk factors

Answer 4

• Children (6-24 years)
• Inadequate sun exposure
• Exclusive breastfeeding without vitamin D supplementation
• Dark skin
• Malabsorption syndromes
• Obesity
• Family history: X-linked hypophosphatemic rickets (XLH), autosomal dominant hypophosphatemic rickets or hypophosphatemic rickets with hypercalciuria (autosomal recessive) disease
• Developing countries

Question 5

Signs

Answer 5

• Bowing of the legs
• Rachitic rosary: a row of beadlike prominences at the junction of a rib and its cartilage (englarged costochondral joints), resembling a rosary.
• Reduced muscle tone
• Harrison’s groove: an indentation on the chest roughly along the 6th rib

Question 6

Symptoms

Answer 6

• Pain in bones or joints
• Muscle weakness
• Drowsiness
• Delayed walking
• Frequent pathological fractures

Question 7

Diagnosis

Answer 7

Primary investigations:
- Serum calcium: typically normal in hypophosphataemic rickets and reduced in calcipaenic rickets
- Serum phosphate: typically reduced in both types of rickets.
- Serum ALP: elevated in both hypophosphataemic and calcipaenic rickets.
- Serum 25-hydroxyvitamin D levels: low with vitamin D deficiency; may be normal or elevated in calcipaenic rickets.
- Serum PTH: elevated due to secondary hyperparathyroidism
- X-rays and bone-density scan: to visualize skeletal deformities, widened growth plates, and areas of decreased bone density
- Urinalysis: To evaluate calcium and phosphate excretion in cases of hypophosphataemic rickets.

Question 8

Treatment

Answer 8

FIRST LINE:
- Vit D supplementation: 1000-2000 units of daily cholecalciferol used to correct the deficiency + improve calcium and phospate absorption
- Calcium supplementation : Provide adequate levels for bone mineralization
- Phosphate supplementation: In cases of hypophosphataemic rickets.

SECOND LINE:
- UVB light exposure: To stimulate endogenous vitamin D synthesis
- Orthopaedic intervention: In severe cases, surgical correction of deformities may be necessary.

Question 9

Complications

Answer 9

• Skeletal deformities
• Growth retardation
• Dental abnormalities
• Bone pain and fractures
• Hypocalcaemic seizures