via Anesthesiology News. Elizabeth A.M. Frost, MD
The ninth in a series of capsules of pertinent information and precautions concerning rare disorders for the anesthesiologist. Click here for full article. Content in post only focuses on achondroplasia.
What Is It?
Achondroplasia is a genetic defect with autosomal dominant inheritance. It may also result from sperm gene mutation in older men. The mutation occurs in the fibroblast growth factor receptor 3 (FGFR3) gene that results in overactivity of the protein. The primary feature of the disease is dwarfism.
Achondroplasia is the most common form of dwarfism. It affects male and female children equally, and is estimated to occur in about one in 27,500 people. Other studies have put the incidence at one in 10,000. Life expectancy is about 10 years less than average. Children who inherit the gene from both parents generally die before or at birth.
Ultrasound can detect achondroplasia in utero. Later DNA tests can confirm the presence of the gene. Confirmation can be made by skeletal survey, showing a large skull, narrow foramen magnum and small skull base with a narrowed spinal canal. The forehead is prominent. Vertebral bodies are typically short. Other characteristic findings include a narrow sciatic notch, short and thick tubular bones, metaphysical cupping and irregular growth plates, with fibular overgrowth and short metacarpals. Legs are bowed in greater than 80% of patients, and thoracolumbar kyphosis is very common. Double-jointedness is common. Abnormality of the midface is seen in greater than 50% of patients, with anteverted nares. Complications include obesity, sleep apnea, hydrocephalus, spinal stenosis and recurrent ear infections. Mental capacity is usually unaffected.
There is no known cure, although the cause of the mutation in the growth factor receptor has been elucidated. In fact, no improvement is seen with human growth after the first or second year of therapy, making it an ineffective long-term treatment. Limb lengthening surgery is controversial, although it may increase leg and arm length. Much of treatment relies on support groups, physical therapy and braces, especially for children who may have decreased muscle tone. Hydrocephalus is a severe complication of achondroplasia and requires shunting or endoscopic third ventriculostomy, often with frequent revisions.
Intravenous cannulation may require ultrasound. Positioning requires special attention due to the bowed legs and kyphosis. Neuraxial anesthesia may prove challenging. Ultrasound-guided combined spinal–epidural anesthesia for elective cesarean delivery has been used successfully. No inhalational agent has been shown to be superior. A difficult airway cart should be available. Any degree of cervical stenosis should be ascertained and appropriate care in intubation taken, with minimal head movement. Narcotic use should be minimized.
Evaluation for sleep apnea should be made and a continuous positive airway pressure or bilevel positive airway pressure machine made available for the postoperative period. Depending on the severity of sleep apnea and the surgery to be performed, same-day surgery might not be warranted. If the patient is presenting for management of hydrocephalus, fluid deficit due to vomiting should be corrected and antiepileptic drugs continued. Infection sources, especially of the ear, should be identified and treated. The electrolyte panel should look for hyperglycemia and be corrected, if necessary.
Patients with achondroplastic dwarfism presenting during pregnancy often require frequent obstetric follow-up visits and invasive prenatal diagnostic tests because of the increased risk for obstetric complications, such as premature delivery and fetal anomalies. A multidisciplinary care team, including an obstetrician, anesthesiologist, pulmonologist, cardiologist and neonatologist, should be available.
Achondroplasia. Genetic and Rare Diseases Information Center. Accessed August 28, 2020. https://rarediseases.info.nih.gov/ diseases/ 8173/ achondroplasia.
Baujat G, Legeai-Mallet L, Finidori G, et al. Achondroplasia. Best Pract Res Clin Rheumatol. 2008;22(1):3-18.
Bouali H, Latrech H. Achondroplasia: current options and future perspective. Pediatr Endocrinol Rev. 2015;12(4):388-395.
Melekoglu R, Celik E, Eraslan S. Successful obstetric and anaesthetic management of a pregnant woman with achondroplasia. BMJ Case Rep. 2017;2017:bcr2017221238.