Most common neonatal lethal skeletal dysplasia (thanatophoric dysplasia (TD))

Thanatophoric dysplasia (TD) is the most common neonatal lethal skeletal dysplasia.

• incidence is approximately one per 20,000 live births
  
  
• most frequent lethal skeletal dysplasia
  
  
• caused by the FGFR3 gene mutation
  
  
• although ultraonography has been used for prenatal diagnosis of TD, occasionally TD fetuses in utero cannot be clearly distinguished from other osteochondrodysplasias
  
  
• term is derived from the Greek word 'thanatophoros,' which means 'death bearing'
  • most common lethal skeletal disorder
    
    
  • two main forms of TD based on the bone deformity pattern
    • Type-1 TD is characterized by short and curved femurs with a telephone-receiver-like appearance, together with very flat vertebral bodies
      • rarely associated with a cloverleaf skull deformity
    • Type-2 TD has straighter femora, but they are just as short
      • characterized by flatter vertebral bodies and is almost always associated with a cloverleaf skull
        
        
  • prenatal diagnosis of TD by ultrasonography has been based on these characteristic shortened limbs or other skeletal defects consistent with TD

Affected individuals die within hours of birth, usually from respiratory failure

• affected neonate usually dies shortly after birth owing to profound pulmonary hypoplasia

Reference:

• Cho I et al. Thanatophoric dysplasia in a dichorionic twin confirmed by genetic analysis at the early second trimester: A case report and literature reviewObstet Gynecol Sci. 2014 Mar;57(2):151-4.