Congenital bone/cartilage disorders

Question 1

Osteogenesis imperfecta type I

Answer 1

Mildest most common, normal life expectancy
Autosomal dominant
Blue sclerae
50% have hearing loss
Fractures before puberty

Question 2

What is osteogenesis imperfecta

Answer 2

Rare disorder (1 in 20,000) of type I collagen resulting in joint laxity + fragile low-density bones

Question 3

Osteogenesis imperfecta type II

Answer 3

Lethal perinatal form
Blue sclera, dwarfism, multiple fractures
Recessive

Question 4

Osteogenesis imperfecta type III

Answer 4

Severe form occurs in 20%
Recessive
Fractures at birth, progressive spinal/limb deformity with short stature
Blue or white sclera with dentinogenesis imperfecta commonly (teeth transparent/discoloured as enamel seperates from dentine)
Life expectancy decreased

Question 5

Osteogenesis imperfecta type IV

Answer 5

Moderate form
Autosomal dominant
Fragile bones
White sclera after infancy

Question 6

Osteogenesis imperfecta imaging

Answer 6

Xray shows many fractures, osteoporotic bones with thin cortex, bone deformity of long bones
Histologically immature unorganised bone

Question 7

Osteogenesis imperfecta treatment

Answer 7

Prevent injury (physio, rehab, OT)
Osteotomies for deformities
IM rods for long bones occasionally
Bisphosphonates for cortical thickness

Question 8

What is achondroplasia

Answer 8

Most common form of disproportionate short stature, caused by reduced growth of cartilaginous bone
Autosomal dominant but ~80% from spontaneous mutation
Gross motor development impaired

Question 9

Achondroplasia XR findings

Answer 9

Short proximal long bones

Wide epiphyses

Question 10

Achondroplasia treatment

Answer 10

Monitoring for potential complications

GH very occasionally tried

Question 11

What is hereditary multiple exostoses

Answer 11

Autosomal dominant disorder where certain proteins accumulate causing cartilage capped tumours at end of long bones, point away from nearby joint
In severe cases bones badly modelled so short stature, forearm/knee/ankle deformity
Can cause malignancy (osteo/chondrosarcoma)

Question 12

Hereditary multiple exostoses treatment

Answer 12

Remove symptomatic exostoses

Question 13

What is osteopetrosis

Answer 13

Lack of differentiation between medulla + cortex (from failure of osteoclastic resorption) causes hard, dense, brittle ‘marble’ bones

Question 14

Osteopetrosis complications

Answer 14

Fractures
Anaemia/thrombocytopaenia from dec marrow space
Deafness/optic atrophy from cranial nerve compression

Question 15

Osteopetrosis imaging features

Answer 15

Variations of ossific density giving bone within bone appearance

Question 16

Joint types

Answer 16

1˚ cartilagenous - Hyaline cartilage between bone ends
2˚ cartilagenous - 1˚ with fibrocartilage between hyaline cartilage
Fibrous - fibrous tissue between bones
Synovial - hyaline cartilage on bone surface with synovial fluid capsule
Synovial atypical - synovial with fibrocartilage on bone surfaces ± fibrocartilage disc e.g. ACJ

Question 17

Bone types

Answer 17

Lamellar - normal bone type
Cancellous (spongy) - type of lamellar
Compact - type of lamellar
Cortical - superficial layer of compact bone

Cartilagenous - formed from growth plates
Endochondral - in cartilage destroyed by calcification

Heterotropic - Forms outside normal skeleton in response to something e.g. surgery
Membranous - formed from intramembranous ossification
Sesamoid - formed in tendon where it passes a joint

Question 18

Osteoporosis pharm treatment

Answer 18

1st - Alendronate - not in oesophageal problems
2nd - Denosumab
3rd - Raloxifene

Question 19

Osteoporosis Diagnosis

Answer 19

FRAX score for 10yr fragility fracture risk

DEXA scan <2.5 is osteoporosis