Achondroplasia is a genetic disorder characterized by abnormal bone growth resulting in short stature, with disproportionately short limbs. Key features include shortening and widening of the long bones, with the proximal segments most affected. Other findings are frontal bossing of the skull, spinal stenosis, recurrent ear infections, and normal intelligence. Diagnosis can be made prenatally by ultrasound or after birth by x-rays showing characteristic bone abnormalities. Treatment may include growth hormone therapy in early childhood, and complications can include spinal stenosis.

1. Achondroplasia
General Considerations
 Autosomal dominant or sporadic mutation disorder of abnormal enchondral bone ossification
 Most common form of short-limbed dwarfism (less than 3rd percentile in standing height)
 In achondroplasia, the extremity involvement is rhizomelic (i.e. proximal) so that the humerus
and femur are more involved than the radius and tibia.
Clinical Findings
 Delayed motor development
 Recurrent otitis media
 Normal intelligence
 Short stature
 Lower extremity radiculopathy
Imaging Findings
 Can be detected before birth by the use of prenatal ultrasound
 After birth, conventional radiography is the study of first choice
 Skull
o Frontal bossing
o Enlarged calvarium and mandible
o Hypoplasia of the midface
 Hands and feet
o Short phalanges
o Fingers of equal length (trident hand)
 Spine
o Narrowing of the interpediculate distance
o Thickening and shortening of the pedicles
 Narrowed AP diameter
o Decreased height of vertebral bodies
 Anterior wedging may produce a “bullet” shape
 Pelvis
o Squared iliac wings
o Narrow sacroiliac notches (Champagne glass appearance)
o Reduced acetabular angle
 Long bones
o Bones are short (rhizomelic) and wide
o Genu varum
o Widening of the metaphyses
o Posterior bowing of the distal humerus
Differential Diagnosis
 Diastrophic Dysplasia
 Spondyloepiphyseal Dysplasia

2. Treatment
Somatotropin (recombinant human growth hormone), especially during years 1-6 of life, may be helpful
Complications
 Spinal stenosis
Prognosis
Life span is usually normal
Achondroplasia. Note squaring of the iliac wings (tombstone pelvis), flattening of the
acetabular angles (yellow arrows), genu varum deformities (white arrows) with widened but
shorter femurs and flaring of the metaphyses (green arrow). Inner pelvis is shaped like a
champagne glass