Bone Dysplasia Definition of Dysplasia Abnormal development Types

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

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 Clinically • Disproportionate dwarfism (most common type)– short limb • AD FGFR 3 mutation • Head • Pseudoachondroplasia normal facies AD chromosome 19 defect on COMP • Affects endochondral > appositonal growth • Physeal dysplasia • Button noses and frontal bossing • Limbs • Rhizomelic – N sitting height • Trident hands • Radial head subluxation • Spine • Lumber stenosis • Thoracolumber stenosis

Conditions Spondyloepeiphyseal dysplasia Mulitiple epiphyseal dysplasia (MED) • Involves the spine caused by • Defect in Type 2 collagen • Congenital type = AD • Tarda type = X-linked • Scoliosis – sharply curved • 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 Mucopolysaccharidosis • Proportionate dwarfism with presence of complex sugars in the urine • Types • Morquio – AR keratin sulphate in urine • C 1/2 instability, cloudy cornea, waddling gait, valgus knees • Wide eyes and wide based stance (monkey) • Hurler – AR heparan/dermatan sulphate • DD rickets with varus knees (N bloods) • Hunter - heparan/dermatan sulphate • Sanilippo - heparin sulphate • Schmid – AD type X collagen • Mc. Kusick – AR cartilage hair dysplasia • Fibular overgrowth and C 1/2 instability • Most severe form with mental retardation