Achondroplasia (ACH) is the most common form of dwarfism, occurring in approximately 1 in 20,000-30,000 live births. This genetic disorder is caused by a change (mutation) in the fibroblast growth factor receptor 3 (FGFR3) gene. Achondroplasia occurs as a result of a spontaneous genetic mutation in approximately 80 percent of patients; in the remaining 20 percent, it is inherited from a parent. This genetic disorder is characterized by an unusually large head (macrocephaly), short upper arms (rhizomelic dwarfism), and short stature (adult height of approximately 4 feet).
Achondroplasia results from specific changes (mutations) of a gene known as a fibroblast growth factor receptor 3 (FGFR3).
Less commonly, familial cases of achondroplasia follow an autosomal dominant pattern of inheritance. Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary to cause a particular disorder. The abnormal gene can be inherited from either parent or can be the result of a mutated (changed) gene in the affected individual. The risk of passing the abnormal gene from an affected parent to an offspring is 50% for each pregnancy. The risk is the same for males and females.
Clinical symptoms of ACH include:
• Disproportionate short stature
• Macrocephaly with frontal bossing
• Backward displacement of the midface and depressed nasal bridge
• Shortening of the arms with redundant skin folds on limbs
• Limitation of elbow extension
• Shortened fingers and toes (brachydactyly)
• Trident configuration of the hands
• Bowed legs
• Exaggerated inward curve of the spine (lumbar lordosis)
• Joint laxity
Recommendations for the manifestations of achondroplasia include:
• Craniocervical junction constriction
• Obstructive sleep apnea
• Middle ear dysfunction
• Short stature
• Varus deformity
• Spinal deformities
• Spinal stenosis