Achondroplasia

Definition

Most common chondrodysplasias in humans. Autosomal dominant trait (fibroblast growth factor receptor-3 gene localized to 4p16.3) with sporatic new mutations observed in 80% increasing in frequency with paternal age. Estimated frequency of 1/14,000–40,000 live births. Characterized by short-limbed (rhizomelia), short trident hands, redundant skin, normal-sized trunk, waddling gait, thoracolumbar gibbous (severe kyphosis), megalocephaly with frontal bossing, low nasal bridge. Radiographs: small cuboid-shaped vertebral bodies, progressive narrowing of the lumbar interpedicular distance, small iliac wings, narrow sciatic notches.

Prognosis

Homozygous infants typically die in infancy from respiratory insufficiency second to a small thorax while mean adult males and females are 130 and 120cm respectively. Despite problems achondroplasia does not incur a shorter life expectancy nor poorer health. Complications arise from hydrocephalus, neuronal compression of such systems as brain...