Diastrophic Dysplasia

Topic updated on 06/24/16 11:09am
  • A form of short-limbed dwarfism caused by failure of formation of secondary ossification center (epiphysis)
    • associated with progressive deformity
  • Epidemiology
    • more common Finland
    • rare in rest of world
  • Genetics
    • autosomal recessive
    • mutation in DTDST gene (SLC26A2) on chromosome 5 
      • encodes for sulfate transporter protein q q    
      • mutation is present in 1 in 70 Finnish citizens
      • leads to undersulfation of cartilage proteoglycan
  • Physical exam and syndrome features
    • short stature ("twisted dwarf")
      • rhizomelic shortening
    • cleft palate (60%)
    • cauliflower ears (80%) 
    • poorly developed UE
    • hitchhikers thumb  q 
    • thoracolumbar scoliosis
    • severe cervical kyphosis 
    • hip and knee contractures
    • genu valgum
    • skewfoot (serpentine or Z foot)
      • tarsometatarsal adductus and valgus hindfoot
    • rigid clubfeet (equinocavovarus) 
  • Radiographs
    • recommended views
      • AP and lateral of cervical spine and thoracolumbar spine
      • three joint standing lower extremity films to assess alignment
  • Ultrasound
    • can be used to make diagnosis prenatally
  • Nonoperative
    • observation and supportive treatment
      • indications
        • most patients
      • modalities
        • cauliflower ears frequently repsond to early treatment with compressive bandages
        • cervical kyphosis frequently resolves spontaneously
  • Operative
    • occipital-cervical fusion
      • indications
        • atlantoaxial instability with neurologic symptoms
          • risk of quadriplegia is a concern
    • posterior cervical fusion
      • indications
        • cervical kyphosis that does not resolve spontaneously
    • thoracolumbar fusion
      • indications
        • kyphoscoliosis of thoracolumbar spine
        • if progressive may require ASF / PSF
    • soft tissue surgical release
      • indications
        • early foot ankle deformity after initial period of casting
        • severe joint contractures (hip and knee)
    • osteotomies for correction
      • indications
        • progressive valgus deformity of lower extremities (with dislocated patellae)
        • resistant or recurrent clubfeet
        • distal femoral extension osteotomies for fixed knee flexion contractures
        • valgus intertrochanteric osteotomies +/- acetabuloplasty for early hip subluxation
    • total joint arthroplasty
      • indications
        • end stage osteoarthritis of hips


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Qbank (4 Questions)

(OBQ12.8) A child with a defect in the DTDST gene would have which of the following classic phenotypes? Topic Review Topic

1. Blue sclera and bowing deformities
2. Mental retardation and cardiac malformations
3. Cauliflower ears and hitchhiker's thumb
4. Craniosynostosis and complex syndactyly
5. Rhizomelic dwarfism and frontal bossing

(OBQ09.49) What is the genetic cause of the dwarfism characterized by a hitchhikers thumb, cauliflower swelling of the ears, and severe clubfeet? Topic Review Topic

1. FGFr-2
2. FGFr-3
3. Sulfate transport protein
4. CBFA-1
5. Gs Alpha Protein

(OBQ05.29) Figure A is a photograph of a newborn's hand. Genetic testing reveals a mutation in the SLC26A2 gene on Chromosome 5q and both the parents were carriers. What condition does this child have? Topic Review Topic
FIGURES: A          

1. Achondroplasia
2. Osteogenesis imperfecta
3. Hypochondroplasia
4. Diastrophic dysplasia
5. Ehlers-danlos syndrome

(OBQ04.104) A 3-year-old child with short-limbed dwarfism has the clinical features shown in Figures A & B. What is the pathoanatomy of this disease? Topic Review Topic
FIGURES: A   B        

1. Sulfate transport protein gene mutation affecting cartilage matrix formation
2. Mutation in the gene CBFA-1 affecting osteocalcin formation
3. Defect in lysosomal-storage
4. Defect in lipid-storage
5. Mutation in gene FGFR-3 resulting in growth plate growth abnormality



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