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Evaluation of a newborn with short limbs is often an urgent challenge for the pediatrician and the neonatologist because of the importance of recognizing lethal neonatal skeletal dysplasias, the ability to provide adequate medical management in nonlethal neonatal skeletal dysplasias, and the ability to provide adequate prognostic information to the family during the stages of the initial evaluation. Sometimes, the diagnosis is evident based on physical examination of the newborn, but more often combined information from prenatal ultrasounds, physical examination of the newborn, and skeletal radiographs and other imaging studies is needed to establish a definitive diagnosis.
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The evaluation and initial treatment of the neonate who has short limbs and a suspected skeletal disorder require a multidisciplinary approach, usually the expertise of a neonatologist, a medical geneticist, and a radiologist. Other specialty services are involved depending on the associated findings, and these experts typically include otorhinolaryngology, plastic surgery, orthopedic surgery, ophthalmology, as well as neurosurgery services.
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Molecular genetic studies are available for some of the more common disorders and can be used to confirm the diagnosis and to provide for a prenatal diagnosis in the future pregnancies of the family, if desired. There are currently more than 400 recognized genetic skeletal disorders, which can be divided into several groups based on molecular, biochemical, or radiographic criteria.1 The molecular etiology is known for approximately 300 of these genetic skeletal disorders,1 providing an opportunity to establish a specific diagnosis and provide accurate prognostic information for the family.
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In addition to genetic etiologies of short limbs in newborns, there are nongenetic causes, such as fetal warfarin exposure, which mimics the skeletal phenotype of chondrodysplasia punctatas,2,3 and maternal diabetes, which has been associated with asymmetric shortening of femoral bones because of proximal focal femoral hypoplasia.4,5 These nongenetic etiologies are important to recognize to be able to provide accurate information regarding recurrence risk and, in cases of a teratogen exposure, to be able to prevent recurrence in future pregnancies.
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PRENATAL ULTRASOUND IN THE EVALUATION AND DIAGNOSIS OF A FETUS WITH SHORT LONG BONES
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Because many skeletal disorders begin to manifest in fetal development, a suspicion of a congenital skeletal disorder will often be raised during an ultrasonographic evaluation of a fetus in the second trimester. The clavicle, mandible, ileum, scapulae, and long bones ossify by 12 weeks of gestation; the metacarpals and metatarsals by 12 to 16 weeks; and the talus and calcaneus around 22–24 weeks, and epiphyseal ossification centers are seen on radiographs around 20 weeks of gestation.6 Some short-limbed skeletal disorders have characteristic findings that can lead to an accurate diagnosis on a prenatal ultrasonographic examination (Table 119-1).7, 8, and 9 Early diagnosis of a fetal skeletal disorder during the prenatal period allows time for genetic counseling, may allow for reproductive options for ...