Week 2. Rickets and Osteomalacia

Question 1

Define the term:

Osteomalacia

Answer 1

Softening of bones resulting from impaired mineralization caused by vitamin D deficiency in adults

Question 2

Define the term:

Rickets

Answer 2

Disturbed bone ossification resulting from impaired mineralisation caused by Vitamin D deficiency in children

Question 3

How is rickets classified? What is the underlying pathological mechanism in each case?

Answer 3

• Vitamin D deficiency - dietry lack, increased intake of phytates, increased phosphate intake, decreased exposure to sunlight, malabsorption syndromes.
• Decreased 25 (OH)2 D3 synthesis - Produced in liver. Therefore liver disease or drugs which affect liver metabolism may cause
• Defective action of 1,25(OH)2D3 - Hormone may be:
  Abnormal - vitamin D administration = curative
  Absent / defective Vitamin D receptors = not curative
• Other - e.g. Familial renal tubular defects etc.

Question 4

Discuss the pathological events occurring in the bones of children who are vitamin D deficient.

Answer 4

• Vit D deficiency ultimately results in decreased Ca2+ levels in bone. This stimulates release of PTH which liberates Ca2+ from bone and increases osteoid content. However, the matrix undergoes defective calcification. This leads to:
  1. Hypertrophy of epiphyseal cartilage – Cartilage not being replaced by bone
  2. Cessation of diaphyseal calcification – Due to low serum Ca2+
  3. Bone resorption in diaphysis – PTH release in attempt to normalize serum Ca2+
• Microfractures resulting in deformity

Question 5

Discuss the signs and symptoms of rickets in:

Neonates

Answer 5

Generic Ssx

i. Restlessness
ii. Poor sleep
iii. Decreased skull mineralization (craniotabes)

Question 6

Discuss the signs and symptoms of rickets in:

Infants

Answer 6

– Missed skeletal landmarks

i. Delayed sitting/crawling
ii. Bossing (rounded eminence) of skull bones
iii. Costochondral beading (rachitic rosary)
iv. Delayed fontanelle closure

Question 7

Discuss the signs and symptoms of rickets in:

1-4 age group

Answer 7

i. Enlargement of epiphyseal cartilages at distal ends of the: radius, ulna, tibia, fibula
ii. Kyphoscoliosis
iii. Bow-legedness
iv. Delayed walking

Question 8

Discuss the signs and symptoms of rickets in:

>4 years

Answer 8

i. Bow legs

ii. Knock knees

Question 9

Distinguish between tetany and tetanus. Define and briefly discuss the term “rachitic tetany”.

Answer 9

• Tetany - is an adjective describing spasms and cramping of the hands, feet and larynx due to low blood calcium levels
• Tetanus - is an acute infectious disease caused by Clostridium tetanus (bacteria) that is characterized by tonic spasm of voluntary muscles, especially jaw muscles (aka lockjaw)
• Rachitic tetany – Tetany due to hypocalcemia accompanying vitamin D deficiency (aka tetany due to rickets)

Question 10

List the radiological findings in rickets

Answer 10

• Widened and irregular epiphyseal growth plates – Due to defective calcification
• Widening of metaphyseal region – Due to pressure on weakened bone
• “Cup shaped” metaphysis – Increased load/stress distributed in the centre, less peripherally
• Spotty rarefaction (reduced density) at diaphyseal ends – Due to bone/Ca2+ resorption
• Cortical thinning – Bone/Ca2+ resorption
• Bone deformity - Bowing of long bones and development of knock knees due to excessive load on softened bones
• Looser zones (pseudofractures) – Characteristic finding of rickets and osteomalacia. Narrow transverse radiolucent lines (2-5mm wide) with sclerotic borders that appear bilateral and symmetric that lie perpendicular to the cortical margins

Question 11

List the radiological findings in Osteomalacia

Answer 11

Osteomalacia – 3D

• Increased radiolucency – Due to demineralization of bone
• Bone deformity – Bowing of long bones, vertical shortening of vertebrae and flattening of pelvis due to excessive load on softened bones
• Looser zones (pseudofractures) – Characteristic finding of rickets and osteomalacia. Narrow transverse radiolucent lines (2-5mm wide) with sclerotic borders that appear bilateral and symmetric that lie perpendicular to the cortical margins

Question 12

Which laboratory investigations are useful in the diagnosis of osteomalacia? Discuss.

Answer 12

• Serum
  o 25(OH)D3 – extremely low. Synthesised from Vit D in liver
  o 1,25(OH)2D3 – extremely low. Synthesised from Vit D in liver
  o Phosphate – Low
  o Alkaline phosphatase – Increased
  o Ca2+ - Low-normal.
  o PTH – Increased (attempt to restore normal serum Ca2+)
  o Urinary Ca2+ - Decreased. Retained in order to normalize serum Ca2+
• Diagnosis
  o Hx of inadequate Vit D intake
  o X-Rays – Look for radiological findings
  o Clinical picture – Look for obvious deformity, Ssx of rickets/osteomalacia
  o Dd’s: Hyperparathyroidism, hyperthyroidism, postmenopausal osteoporosis, Cushing’s syndrome