Bone Dysplasia

Definition of Dysplasia • Abnormal development • Types• Proportionate dysplasia /

dwarfism • Disproportionate

• Short trunk eg Kniest syndrome• Short limb

• Proximal – rhizomelic• Middle – mesomelic• Distal – acromelic

Proportionate eg mucopolysaccharidoses

Definition of Dysplasia • Abnormal development • Types• Proportionate dysplasia /

dwarfism • Disproportionate

• Short trunk eg Kniest syndrome• Short limb

• Proximal – rhizomelic• Middle – mesomelic• Distal – acromelic

Disproportionate

Definition of Dysplasia • Abnormal development • Types• Proportionate dysplasia /

dwarfism • Disproportionate

• Short trunk eg Kniest syndrome• Short limb

• Proximal – rhizomelic• Middle – mesomelic• Distal – acromelic

Disproportionate

Definition of Dysplasia • Abnormal development • Types• Proportionate dysplasia /

dwarfism • Disproportionate

• Short trunk eg Kniest syndrome• Short limb

• Proximal – rhizomelic• Middle – mesomelic• Distal – acromelic

Disproportionate

Definition of Dysplasia • Abnormal development • Types• Proportionate dysplasia /

dwarfism • Disproportionate

• Short trunk eg Kniest syndrome• Short limb

• Proximal – rhizomelic• Middle – mesomelic• Distal – acromelic

Disproportionate

Classification based on growth plate

Hyperplasia • Epiphysis • Physis • Hyperchondroplasia • Enchondromatosis

• Metaphysis • Exostosis

• Diaphyseal• Progressive diaphyseal dysplasia

Hypoplasia • Epiphysis

• Spondyloepiphyseal dysplasia• Multiple epiphyseal dysplasia

• Physis • Achondroplasia

• Metaphysis • Hypophosphatasia• Osteopetrosis

• Diaphyseal• OI and osteoporosis

Conditions

Achondroplasia• Disproportionate dwarfism (most

common type)– short limb • AD FGFR 3 mutation

• Pseudoachondroplasia normal facies AD chromosome 19 defect on COMP

• Affects endochondral > appositonal growth • Physeal dysplasia

Clinically• Head

• Button noses and frontal bossing

• Limbs • Rhizomelic – N sitting height • Trident hands• Radial head subluxation

• Spine• Lumber stenosis • Thoracolumber stenosis

Conditions

Spondyloepeiphyseal dysplasia • Involves the spine caused by • Defect in Type 2 collagen • Congenital type = AD• Tarda type = X-linked• Scoliosis – sharply curved

Mulitiple epiphyseal dysplasia (MED) • Mutation in COMP • Delayed ossification / irregular

epiphyses• Clinically limb abnormalities• Short MC and MT• Valgus knees • Irregular proximal femora

Conditions

Kniest Syndrome• AD defect in collage type II• Short trunk disproportionate

dwarfism• Clinically

• Orthopaedic• Contractures/stiffness• Scoliosis and kyphosis• Dumbbell femora

• Extra-skeletal• Otitis media and hearing loss

Dysplasia Epiphysealis Hemimeilica (trevors disease)• Epiphyseal osteochondromata• Calcifications also seen within

joint • Usually only affects 1 joint

Conditions

Metaphyseal Chondrodysplasia • Affects proliferative and

hypertrophic zones of physis• Types

• Jansen – AD defect to parathyroid related hormone • Wide eyes and wide based stance

(monkey)• Schmid – AD type X collagen

• DD rickets with varus knees (N bloods) • McKusick – AR cartilage hair dysplasia

• Fibular overgrowth and C1/2 instability

Mucopolysaccharidosis • Proportionate dwarfism with presence

of complex sugars in the urine• Types

• Morquio – AR keratin sulphate in urine• C1/2 instability, cloudy cornea, waddling

gait, valgus knees• Hurler – AR heparan/dermatan sulphate

• Most severe form with mental retardation• Hunter - heparan/dermatan sulphate • Sanilippo - heparin sulphate