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Disproportionate Dwarfism Flashcards

Achondroplasia Pseudoachondroplasia Multiple Epiphyseal Dysplasia Spondyloepiphyseal Dysplasia Diastrophic Dsyplasia Kneist's Dysplasia Metaphyseal Dysplasia

1
Q

What is achondroplasia?

A
  • The most common cause of disproportionate dwarfism
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2
Q

What is the genetics of achondroplasia?

A
  • Autosomal dominant
  • caused by mutation of fibroblast growth factor receptor 3 (FGFR3) on chromosome 4P
  • changes lysine to argentine at position 380
  • sporadic mutation in >80% cases
    • Risk increases with advanced paternal age
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3
Q

What does this gene mutation cause?

A
  • Abnormal chondroid production by chondroblasts in the PROLIFERATIVE ZONE during enchondral bone formation at the physis
  • A quantative rather than qualitative cartilage defect
  • sporadic mutation in 80% cases
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4
Q

What is the conditions is achondroplasia associated with?

A
  • Lumbar stenosis
    • short pedicles
    • most likely to cause disability
  • Thoracolumbar kyphosis
    • may cause neurological symptoms
  • Foramen magnum and upper cervical stenosis
    • may cause periods of apnea
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5
Q

What is pseudoachondroplasia?

A
  • An autosmal dominant condition that is clinically similar to achondroplasia
  • caused by a defect in the Cartilage Oligomeric Matrix Protein (COMP) on chromosome 19
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6
Q

How does pseudoachondroplasia differ form achondroplasia?

A

Pseusoachondroplasia has

  • Normal facies
  • associated with CERVICAL INSTABILITY due to ondontoid hypoplasia,
  • absence of spinal stenosis
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7
Q

What are the symptoms of achondroplasia?

A
  • Normal IQ
  • Delayed motor milestones
  • Symptoms of spinal stenosis
    • pseudoclaudication and standing discomfort
    • Numbness and parathesia
    • Subjective weakness
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8
Q

What is this

A
  • A trident hand
  • Characterstic splaying of 2-4th digits along the ap axis in the plane of the palmwith relatively normal positioning of thumb and little finger
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9
Q

What are the physical feature of Achondroplasia?

A
  • Classic RHIZOMELIC dwarfism
    • humerus and femurs shorter than forearms and tibia
      • adult height 50 inches
      • NORMAL trunk
  • Facial features
    • frontal bosssing
    • button noses
    • small nasal bridges
  • Hands
    • TRIDENT- inabilty to approixmate extended middle and ring fingers
    • Bowed legs
    • radial head subluxation
    • muscular hypotonia
  • spine
    • thoracolumbar kyphosis
    • excessive lordosis- short predicles
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10
Q

What are the X-ray appearance of pelvis in achondroplasia ?

A
  • Pelvis
    • champagne glass pelvis - wider than deep, flattened acetabulum, square iliac wings
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11
Q

What is this?

A
  • Posterior Vertebral Scalloping
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12
Q

What is seen on the spinal radiographs?

A
  • short pedicles with decreased interpedicular distance form L1-S1
  • T12/L1 vertebral wedging
  • posterior spine scalloping
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13
Q

What is the tx for spinal kyphosis?

A

non op bracing operative- anterior strut corpectomy and post fusion if kyphosis >60 degrees

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14
Q

When in MRi useful in achondroplasia?

A
  • to evaluate Cervical stenosis
  • suspected foramen magnum stenosis
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15
Q

What is the tx of spinal kyphosis in achondroplasia?

A

non operative

  • bracing
  • first line in mild curves

Surgery

  • Anterior strut corpectomy and posterior fusion
    • when kyphosis >60o by 5 yrs
    • bracing failed
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16
Q

What is the tx for foramen magnum stenosis in achondroplasia?

A

Surgery

  • Urgent decompression
  • when cord compression is present
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17
Q

What is the tx for lumbar stenosis in achondroplasia?

A

Non operative

  • Weight loss, physical therapy, corticosteriod injections

Surgery

  • mutlilevel LAMINECTOMY and fusion
  • w spinal stenosis w severe symptoms
  • non op mx failed
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18
Q

What is the tx for short stature in achondroplasia?

A

Surgery

  • Limb lengthening thru metaphyseal corticotomy- controversial due to high risk of complications
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19
Q

What is the tx for genu varum in achondroplasia?

A

Surgery

  • Tibial osteotomies or hemiepiphysiodesis
    • symptoms are severe
    • non op modalities have failed
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20
Q

What is Multiple epiphyseal dysplasia (MEN)?

A
  • a form of dwarfism characterized by Irregular, delayed ossification at multiple epiphyses
  • caused by failure of formation of secondary ossification centre ( epiphysis)
21
Q

Describe the genetics of Multiple epiphyseal dysplasia?

A
  • Autosomal Dominant
  • Defect in cartilage oligomeric matrix protein (COMP) on chromosome 19- most common & severe form
  • mutations in COL9A1, COL9A2, COL9A3
    • codes for type IX collagen
    • causes Type 2 collagen dysfunction because of type IX collagen acts as a link protein for type 2 collagen

***NB MEN in white COLLars**

22
Q

What are the symptoms of pts with Multiple epiphyseal dysplasia?

A
  • short limbed dwarfism
  • Joint pain
  • Often don’t manifest until ages 5-14 yrs
  • waddling gait

Signs

  • joint deformities from joint incongruity
    • Valgus knee common
    • early OA
  • Joint contractures common
  • spine usually normal
23
Q

What is seen on pelvic radiographs with Multiple epiphyseal dysplasia?

A
  • Bilateral epiphyseal defects
    • may mimic Legg-calves perthes
    • difference in Multiple epiphyseal dysplasia is hips are simultaneous and bilateral
24
Q

What is seen in knee xrays w Multiple epiphyseal dysplasia?

A
  • Valgus knee
  • tibial “slant sign”
  • Double layer patella
25
What is seen in hand and foot xrays in Multiple epiphyseal dysplasia?
Hand * short, shunted/broad metacarpals * hyperextensible fingers Foot * Short metatarsals
26
What is the tx of Multiple epiphyseal dysplasia?
_Non operative_ * **NSAIDS and PT** * early OA _Sugery_ * **Corrective osteotomy or hemiepiphysiodesis** * progressive genu valgum * **Total hip replacement** * severe arthritis * joint incongruity may lead to early arthritis & often requires THR early on in life
27
What is spondyloepiphyseal Dsyplasia
* A form of **short- trunk dwarfism** caused by a defect in **the secondary ossification centre** (epiphysis)
28
What is the epidemiology of spondyloepiphyseal Dsyplasia?
* 1 per 100,000 live births * risk factors * advanced Paternal age * familial inheritance
29
what is the pathophysiology of spondyloepiphyseal Dsyplasia?
* Caused by **abnormal synthesis** of **TYPE 2 collagen** * primarily affects the **Vertebra and epiphysis of bone**
30
Describe the genetics of spondyloepiphyseal Dsyplasia?
* **Autosomal Dominant** - SED congenita * **X linked recessive** - SED tarda * **random mutation 50% cases** * Mutations * **​COL2A1 on chromosome 12**
31
Name the assocaited conditions of spondyloepiphyseal Dsyplasia
* **atlantoaxial instability** * Frequent cause of myelopathy in spondyloepiphyseal Dsyplasia congenita * nephrotic syndome (SED Tarda)
32
What is the classificaiton of spondyloepiphyseal Dsyplasia?
* **SED congentia** * Autosomal Dominant * More Severe than tardia * **SED tarda** * **​X linked recessive** * **clinically less severe ** * **doesn;t have lower extremity angular deformities that are present in congenita form**
33
What are the symptoms of a pt with spondyloepiphyseal Dsyplasia?
* **Cervical myopathy** * due to atlantoaxial instability * **respiratory Difficulty** * respiratory insufficiency 2ary to thoracic dysplasia * **Problems with vision** * due to myopia or retinal detatchment * **Hip pain** * **​**due to coxa vara * **decreased walking distance** * due to poor muscular endurance adn skeletal deformities
34
What are the signs of spondyloepiphyseal Dsyplasia?
* **Short stature** * **Flattened Facies** * Kyphoscoliosis * Lumbar lordosis * coxa vara * genu valgum * Wadlling gait * reduced rom of hips
35
What is seen in xrays of c psine in spondyloepiphyseal Dsyplasia?
* Upper cervical spine instability * odontoid hyperplasia or os odontoideum
36
What is seen on thoracolumbar spine xrays in spondyloepiphyseal Dsyplasia?
* **Platspondyly** * flattening of vertebral bodies in lumbar spine * incomplete fusion of spinal ossification centres * end plate irregularities and narrowed intervertebral disc spaces * kyphoscoliosis * excessive lumbar lordosis
37
What is the tx of spondyloepiphyseal Dsyplasia?
* **mutlidisciplinary rehabilitation** * all pts to maintain and improve function * PT/OT/ortho ( bracing), respiratory, ophalamolgist _Surgery_ * **Posterior atlantoaxial fusion** ( post instrumentation) * atlantoaxial instability \>8mm * myelopathy * **Posterior thoracolumbar instrumentation** * spinal scoliosis \>50o * distraction spinal rods- ypunger pts * post instrumented fusion older pts * **Valgus intertroachanteric ostoetomy** * Coxa vara \<110 o * progressive coxa vara * symptomatic hip arthritis
38
What are the complications of spondyloepiphyseal Dsyplasia?
* **Cervical spine instability** * **Spinal deformity** * including scoliosis, kyphosis, lordosis * **Ocular abnormalities** * **Hip deformities** * **Degenerative Joint disease**
39
What is Diastrophic dysplasia?
* A form of **short limb dwarfism** * caused by **failure of formation of secondary ossification centre** (epiphysis) * associated with **progressive deformity**
40
What is the epidemiology of Diastrophic dysplasia?
* More common in Finland * Rare rest of world
41
What is the genetics of Diastrophic dysplasia?
* **Autosomal Recessive** * **Mutation of DTDST gene **(SLC26A2) on chromosome **5q** * encodes for **sulphate transporter protein** * Mutation is present in 1 in 70 Finnish citizens * leads to **undersulfation of catilage proteoglycan** * **abnormalities in the hydraulic properties of cartilage=** **why cartilagneous structures affected -ears, trachea and ligaments**
42
what are the signs of a child with diastrophic dysplasia?
* **Short stature**- twisted dwarf * **rhizomelic** shortening * `cleft palate- 60% * Cauliflower ears 80% * Poorly developed UE * **Hitchhikers thumb** * thoracolumbar scoliosis * Severe cervical kyphosis * hip and knee contractures * Genu Valgum * Skewfoot ( serpentine or z foot) * tarsometatarsal adductus & valgus hindfoot * Rigid clubfoot- equinocavovarus
43
What is the tx of dystrophic dysplasia? ## Footnote
Non operative * **Observation and supportive tx** * most pts * cauloflower ears respond to compressive bandages * cervical kyphosis frequently resolves spontaneously Surgery * **Occipital-Cervical fusion** * Atlantoaxial instability w neuro symptoms * risk of quadariplegia is concern * **Post cervical fusion** * Cervical kyphosis that doesn't resolve spontaneously * **Thoracolumbar fusion** * kyphoscoliosis of thoracolumbar spine * if progressive may require ASF/PSF * **Soft tissue surgical release** * rigid clubfoot * severe joint contractures hip/knee * **Osteotomies for correction** * for *progressive valgus deformity of lower extremities* ( w dislocated patella) * **Total joint arthroplasty** * end stage arthritis
44
Define Kniest's Dysplasia?
* **Form of disproportinate dwarfism** * **Autosomal Dominant** * defects leads to abnormal **Type 2 collagen**
45
What is Kniest's dysplasia associated with?
* respiratory problems * cleft palate * **Retinal detachment/ myopia** * **otitis media w hearing loss**
46
Describe the features of Kniest's dysplasia?
* Disproportinate short-trunk dwarfism * **Joint stiffness/ contractures** * **dumbell shaped femora** * Hypoplastic pelvis and spine * scoliosis and kyphosis * cleft lip
47
What is seen on xrays in Kniest's dysplasia?
* **Osteopenia** * **Dumbell femora**
48
What is the tx of Kniest's dysplasia myopia, joint contractures, joint degeneration?
* Myopia= ophthalmolgic consultattion * Joint contractures- early PT * Hip degenertaive arthritis= joint reconstruction
49
What is metaphyseal chondrodysplasia?
* Short limbed disproportinate dwarfism * Involves the proliferative and hypertrophic zones of the physis * 3 types * **Jansen's** * **​**AD, defect in parathyroid hormone related peptide receptor * Low IQ, wide eyes, monkey like stance * osteobulbous metaphyseal expansion of long bones * **Schmid** * **​AD , defect in type X collagen** * xs lumbar lordosis, severe thigh/leg bowing genu varum, wrist swelling * **Mckusicks** * **​AR seen** in amish pop and in Finland * cartilage hair dysplasia, atlantoaxial instability, ankle deformity due to fibular overgrowth, immuno def and increased risk of malignancy

Paediatrics FCRS (27 decks)

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