Symptoms of Achondroplasia 1. General This rare genetic disorder is characterized by distinctive features: short stature (usually under 4 feet 6 inches); an unusually large head (macrocephaly) with a prominent forehead (frontal bossing) and flat (depressed) nasal bridge; short arms and legs; prominent abdomen and buttocks (due to inward curve of the spine); and short hands with fingers that assume a "trident" or three-pronged position during extension. 2. Infancy Infants born with achondroplasia typically have a "dome-like" (vaulted) skull, and a very broad forehead. In a small proportion there is excessive accumulation of fluid around the brain (hydrocephalus). Low muscle tone (hypotonia) in infancy is typical of achondroplasia. Acquisition of developmental motor milestones may be delayed.