Cardinal features include short stature, rhizomelic shortening of the arms and legs, a disproportionately long trunk, trident hands, midfacial hypoplasia, prominent forehead (frontal bossing), thoracolumbar gibbus, true megalencephaly, and caudal narrowing of the interpedicular spaces.
Sudden death in the first year of life is attributed to abnormalities at the craniocervical junction causing spinal cord compression. The rate of unexpected death in infants with achondroplasia is less than 3%.
Angular deformities of the extremities, premature degenerative joint disease, and spinal disorders are common clinical features.
Cervical instability, a potentially life-threatening dysplasia, occurs in a large percentage of patients.
Respiratory disorders are seen frequently, including apnea and abnormalities of gas exchange. Studies report that as many as 75% of children with achondroplasia have a pathologic apnea index (>30 episodes).
Brainstem compression may contribute to central apnea, and obstructive apnea may be related to midface abnormalities.
Restrictive pulmonary disease, with or without restrictive airway disease, occurs in fewer than 5% of children younger than 3 years.
Tonsillectomy and adenectomy do not yield satisfactory results in these children as in other children, possibly because in addition to adenotonsillar hypertrophy, hypotonicity and a narrowed body confining the airway may contribute to upper airway obstruction in children with achondroplasia.
As seen in other children with obstructive sleep apnea (OSA), in children with achondroplasia, respiratory dysfunction detected in polysomnograms is associated with cognitive deficits.
Sudden death in the first year of life is attributed to abnormalities at the craniocervical junction causing spinal cord compression. The rate of unexpected death in infants with achondroplasia is less than 3%.
Angular deformities of the extremities, premature degenerative joint disease, and spinal disorders are common clinical features.
Cervical instability, a potentially life-threatening dysplasia, occurs in a large percentage of patients.
Respiratory disorders are seen frequently, including apnea and abnormalities of gas exchange. Studies report that as many as 75% of children with achondroplasia have a pathologic apnea index (>30 episodes).
Brainstem compression may contribute to central apnea, and obstructive apnea may be related to midface abnormalities.
Restrictive pulmonary disease, with or without restrictive airway disease, occurs in fewer than 5% of children younger than 3 years.
Tonsillectomy and adenectomy do not yield satisfactory results in these children as in other children, possibly because in addition to adenotonsillar hypertrophy, hypotonicity and a narrowed body confining the airway may contribute to upper airway obstruction in children with achondroplasia.
As seen in other children with obstructive sleep apnea (OSA), in children with achondroplasia, respiratory dysfunction detected in polysomnograms is associated with cognitive deficits.
Perform a skeletal survey. Plain x-ray films obtained at birth can identify achondroplasia. Features include a contracted skull base, square-shaped long bones, trident hands, normal trunk length, proximal femoral radiolucency, and chevron-shaped distal femoral epiphysis. Growth plates are shortened.
When disproportionately short limbs are observed in the fetus on ultrasonography, plain film radiography performed after delivery may distinguish achondroplasia from other conditions.
MRI: MRI findings combined with somatosensory-evoked potentials can reveal spinal stenosis in the lumbar spine or foramen magnum.
Ultrasound
Perform head ultrasonography at birth and at ages 2 months, 4 months, and 6 months to monitor ventricular size for possible hydrocephalus and possible intracranial bleeding. In addition, perform ultrasonography if the fontanel is unusually large, the occipitofrontal circumference increases disproportionately, or symptoms of hydrocephalus develop.
Routine fetal ultrasonography is performed during prenatal visits of most pregnancies, even in low-risk pregnancies. In achondroplasia, ultrasonography is recommended for prenatal diagnosis if requested. Perform fetal ultrasonography to evaluate skeletal anomalies and to measure the long bones for size, shape, bowing, symmetry, and quality of calcification. Obtain serial ultrasonographs at the beginning of the second trimester to plot the femoral length growth curves to distinguish individuals with homozygous (lethal) and heterozygous (nonlethal) achondroplasia from unaffected individuals
When disproportionately short limbs are observed in the fetus on ultrasonography, plain film radiography performed after delivery may distinguish achondroplasia from other conditions.
MRI: MRI findings combined with somatosensory-evoked potentials can reveal spinal stenosis in the lumbar spine or foramen magnum.
Ultrasound
Perform head ultrasonography at birth and at ages 2 months, 4 months, and 6 months to monitor ventricular size for possible hydrocephalus and possible intracranial bleeding. In addition, perform ultrasonography if the fontanel is unusually large, the occipitofrontal circumference increases disproportionately, or symptoms of hydrocephalus develop.
Routine fetal ultrasonography is performed during prenatal visits of most pregnancies, even in low-risk pregnancies. In achondroplasia, ultrasonography is recommended for prenatal diagnosis if requested. Perform fetal ultrasonography to evaluate skeletal anomalies and to measure the long bones for size, shape, bowing, symmetry, and quality of calcification. Obtain serial ultrasonographs at the beginning of the second trimester to plot the femoral length growth curves to distinguish individuals with homozygous (lethal) and heterozygous (nonlethal) achondroplasia from unaffected individuals
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