Achondroplasia (Classic Chondrodystrophy)

Key Features

• Most common form of short-limbed dwarfism

• Upper arms and thighs are proportionately shorter than the forearms and legs

• Skeletal dysplasia is suspected based on abnormal stature, disproportion, dysmorphism, or deformity

• Measurement of height is an excellent clinical screening tool

• While this disorder has an autosomal dominant transmission pattern, 80% of cases result from a random mutation in the fibroblast growth factor receptor-3 (FGFR3) gene

Clinical Findings

• Bowing of the extremities

• Waddling gait

• Limitation of motion of major joints

• Relaxation of the ligaments

• Short stubby fingers of almost equal length

• Frontal bossing

• Midface hypoplasia

• Otolaryngeal system dysfunction

• Moderate hydrocephalus

• Depressed nasal bridge

• Lumbar lordosis

• Intelligence and sexual function are normal

Diagnosis

• Radiographs demonstrate short, thick tubular bones and irregular epiphysial plates

• Ends of the bones are thick, with broadening and cupping

• Epiphysial ossification may be delayed

• Due to diminished growth in the spinal pedicles, the spinal canal is narrowed (congenital stenosis)

• Herniated disk in adulthood may lead to acute paraplegia

Treatment

• Growth hormone is given to some children with bone dysplasia

• Limb lengthening is possible to achieve a more normal proportion of extremities but is controversial