Type
Disproportionate dwarfism with a short trunk
Problems with dwarfism, spine, vision and hearing
Definition
Primary involvement of vertebrae & epiphyseal centres of limbs
Resulting short-trunk dwarfism
- Limb are short, but trunk is even shorter
(cf Metaphyseal Chondrodysplasia - Short limbed Dwarf)
Types
Congenita
- AD, usually spontaneous mutation
- more severe, early
Tarda
- X linked recessive
- late presentation
- spine and hips
Pathology
Defect Type II Collagen Gene
- Disorder of growth plate
- Abnormality of Proliferative zone - Microcystic areas
- Surrounded by ring of abnormal chondrocytes
Clinical Features
Short limbs
- Rhizomelic - short proximal segment
- Normal hands & legs
Shorter trunk
- Neck almost absent
Hip FFD
- Increases lumbar lordosis
Genu valgum
Club foot
Adolescent kyphoscoliosis
Also
- Cleft palate
- Pectus carinatum & barrel-shaped chest
- Protruberant abdomen
DDx
Morquio's disease
- But shortening in distal limb segments (acromelic)
- Urinalysis = Keratan Sulphate excretion
- hands and feet severely affected
Achondroplasia
- normal trunk
- abnormal face
- nil platyspondyly
- rhizomelia - short long bones
Medical Complications
Eye problems common
- Myopia
- Retinal detachment
Radiology
Epiphyses appear late (like MED)
Spine
Platyspondyly
- Flatten or oval vertebral bodies
Schmorl's nodes - indentations of end plates
Irregularity of the vertebral bodies ring epiphyses
Odontoid hypoplasia
Thoracic kyphoscoliosis
- Usually progresses and should be braced early, may need fusion
Lumbar lordosis
Neck
Odontoid hypoplasia
- atlantoaxial subluxation
- Cord compression result in cervical myelopathy
Treat with posterior atlantoaxial or occipitoaxial fusion
Hip
Delayed ossification of capital femoral epiphysis
- Coxa vara - valgising IT osteotomy
- Varus may progress to discontinuity of femoral neck
- May be progressive dislocation