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A prenatal ultrasound at 28 weeks shows shortened long bones (rhizomelic shortening) with a relatively large head and frontal bossing. Parents are average height.
AD; FGFR3 (fibroblast growth factor receptor 3)
- c.1138G>A (p.Gly380Arg) in ~98%
- Gain-of-function variant (constitutive receptor activation)
- ~80% de novo; associated with advanced paternal age
- Rhizomelic (proximal) limb shortening
- Macrocephaly, frontal bossing, midface hypoplasia
- Trident hand configuration
- Lumbar lordosis, thoracolumbar kyphosis
- Average adult height: ~4 feet (122-132 cm)
- Normal intelligence
Complications:
- Foramen magnum stenosis (apnea, sudden death in infancy)
- Spinal stenosis (adults)
- Recurrent otitis media
- Obstructive sleep apnea
- Clinical and radiographic recognition: rhizomelic short stature, characteristic facies, trident hands
- Skeletal survey: short tubular bones, narrowing interpedicular distance caudally in lumbar spine, squared iliac wings, "champagne glass" pelvis
- Confirmatory FGFR3 targeted testing (c.1138G>A in ~98%)
- Frequently suspected prenatally on third-trimester ultrasound (short long bones, macrocephaly, frontal bossing)
- Vosoritide (C-type natriuretic peptide analog) - FDA approved for growth