Achondroplasia is a genetic condition affecting bone growth, leading to short stature and characteristic changes in limb, skull, and spine development. It is the most common form of disproportionate dwarfism. Individuals with achondroplasia have normal intelligence, and life expectancy is near normal, though they face specific health and surgical challenges.

Genetics and Pathophysiology

Achondroplasia arises from a mutation in the FGFR3 gene. The mutation causes the FGFR3 protein to be overactive, which slows down the conversion of cartilage into bone (endochondral ossification), especially in the growth plates of long bones. This impaired bone growth leads to the shorter limbs seen in the condition. In most cases, the mutation is new (not inherited).

Growth is affected early. Long bones (for example, the humerus and femur) grow less than expected, particularly the upper segments (proximal parts). The skull and trunk are less severely affected in proportion.

Epidemiology

Achondroplasia occurs in approximately 1 in 15,000 to 1 in 40,000 live births. The condition is autosomal dominant, meaning one altered gene copy is sufficient to express the disorder. In over 80 percent of cases, the affected individual is born to parents of average height, due to a spontaneous mutation. When a parent has achondroplasia, there is about a 50 percent chance of passing it to the child. If both parents have achondroplasia, there is a risk of a more severe form, which may not be compatible with life.

Clinical Features

Physical Characteristics

From birth or infancy, features may include:

• Short stature, with rhizomelic shortening (upper parts of limbs shorter relative to lower parts)
• Disproportion between limb length and trunk, with trunk near average size
• Enlarged head with prominent forehead (frontal bossing), midface underdevelopment, flattened nasal bridge
• Hands that may show a trident configuration (middle fingers separated)
• Bowed lower legs (genu varum)
• Spinal curvatures: lumbar lordosis and thoracolumbar kyphosis early in life; often exaggerated as the child grows
• Loose joints in some areas; restricted elbow extension

Related Health Problems

Besides bone growth differences, there are several potential complications:

• Delays in motor skills (sitting, walking) due to hypotonia and limb shortening
• Frequent ear infections and risk of hearing loss
• Obstructive sleep apnea due to airway anatomy
• Narrowing of the spinal canal (spinal stenosis), which may compress nerves or the spinal cord
• Compression at the foramen magnum (base of skull) in infancy, which may affect breathing or cause hydrocephalus
• Tendency toward obesity, which can worsen joint and back problems
• Dental crowding, teeth misalignment

Diagnostic Evaluation

Diagnosis is usually possible at or following birth based on clinical examination and characteristic appearance. Imaging (X-rays) helps define bone growth, verify limb proportions, detect spinal changes, and assess the skull base.

Prenatally, ultrasound may suggest shorter limb lengths and an enlarged head; genetic testing may confirm the FGFR3 mutation in higher-risk families.

Ongoing monitoring is important for growth (height, head circumference), for signs of spinal compression or other complications, and to guide any surgical or supportive interventions.

Management

There is no cure for achondroplasia, and treatment focuses on managing complications, optimizing function, and improving quality of life.

Non-surgical / Supportive Care

• Regular monitoring of growth, weight, and head size using growth charts specific to achondroplasia
• Nutritional support and lifestyle changes to prevent obesity
• Physical therapy to improve strength, flexibility, and mitigate delays in motor milestones
• Treatment of ear infections to reduce the risk of hearing loss

Surgical and Other Interventions

• If foramen magnum compression is present or severe, surgery to relieve pressure may be required
• For spinal stenosis, decompression procedures may be needed later in life
• Treatment of associated conditions such as sleep apnea (e.g., airway surgery or use of CPAP)
• Orthopedic correction of limb deformities (for example, bowing) or spine curvature if severe and affecting function
• Growth-promoting therapies: certain novel medications approved for children over a certain age have been shown to increase annual growth; still under study to determine long-term effects

Prognosis

Individuals with achondroplasia can live full lives. While average adult height is considerably below typical norms, most achieve good mobility and independence. Functional ability depends on the severity of complications, the degree of medical and surgical management, and support systems.

Lifespan is near normal, though some increase in risk of early death related to complications (for example, brainstem compression) is seen in infancy. Quality of life may be influenced by joint pain, spinal problems, hearing issues, and obesity.

Prevention and Patient Education

• Genetic counseling is recommended for affected individuals or families with a history of achondroplasia
• Early detection of complications and prompt management (for spinal issues, airway problems, ear infections) can improve outcomes
• Multidisciplinary care involving orthopaedics, genetics, neurosurgery, ENT, pulmonology, and physical therapy helps address the variety of challenges
• Encouragement of healthy weight and physical activity within safe limits

References

Chintapalli R, Desai A. Achondroplasia Status and Adverse Short-Term Postoperative Outcomes in Elective Spinal Decompression Surgery: A Propensity Score-Matched Case-Control Study. J Clin Neurosci. 2025 Apr;134:111064. doi: 10.1016/j.jocn.2025.111064. Epub 2025 Jan 30. PMID: 39889523.

Merchant N, Alvir J, Ericksen PN, Loftus J, Cara JF, Slade A, Wajnrajch MP, Baker CL. Clinical and economic burden of achondroplasia in the United States: results from a retrospective, observational study. Orphanet J Rare Dis. 2025 Feb 27;20(1):90. doi: 10.1186/s13023-024-03268-w. PMID: 40016839; PMCID: PMC11869590.

Vallin AL, Grévent D, Bessières B, Salomon LJ, Legeai-Mallet L, Cormier-Daire V, Baujat G, Ville Y, Faure-Bardon V. Foetal achondroplasia: Prenatal diagnosis, outcome and perspectives. J Gynecol Obstet Hum Reprod. 2025 Feb;54(2):102891. doi: 10.1016/j.jogoh.2024.102891. Epub 2024 Dec 5. PMID: 39643117.