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Radial ray anomalies and associated malformations range from unilateral, sporadic defects to bilateral defects that are associated with multiple malformation syndromes.
Three-dimensional imaging can improve visualization of subtle anomalies of the limbs and provide clearer imaging of the anomalies that can be helpful when counseling patients and families.
Radial ray defects can be isolated or syndromic and associated with multiple anomalies. Abnormalities of any organ system, including musculoskeletal, spinal, cardiothoracic, gastrointestinal, or genitourinary, can be associated with radial ray defects.
Differential Diagnosis
The differential diagnosis depends on the type of anomalies and whether the findings are isolated or associated with other malformations.
Common associations include the following findings:
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VACTERL (Vertebral defects, Anal atresia, Cardiac defects, TracheoEsophageal fistula, Renal anomalies, and Limb abnormalities, specifically of the radial ray) association
: Bilateral absence of radii with thumbs present (thrombocytopenia develops in utero or within first few months of life; this syndrome can include other skeletal, cardiac, and genitourinary anomalies).
: Radial ray defect (49%) and genitourinary, skeletal, gastrointestinal, and central nervous system abnormalities; café-au-lait spots (skin pigmentation abnormalities caused by melanin deposition) are common, and progressive bone marrow depletion leads to transfusion-dependent anemia in the first two decades of life.
: Fetal valproate syndrome is the most common teratogenic syndrome associated with radial ray malformation; this syndrome includes limb and facial anomalies and cognitive delays.
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Ectrodactyly: Absence or deficiency of ≥1 digits; it often is associated with cleft lip with or without cleft palate but rarely is associated with radial ray defects.
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Amniotic band syndrome: Constrictive rings of fibrous tissue that generally appear as amputated limbs.
Genetic Evaluation
Diagnostic testing (amniocentesis or chorionic villus sampling) with chromosomal microarray analysis (CMA) should be offered when a radial ray malformation is detected. If screening or other ultrasound features are suggestive of a common aneuploidy, it is reasonable initially to perform karyotype analysis or fluorescence in situ hybridization, with reflex to CMA if these test results are normal. Many syndromes are associated with radial ray malformations; they can be sporadic, autosomal dominant, autosomal recessive, or X-linked. If there are additional anomalies, consanguinity, or a family history of a specific condition, gene panel testing or exome sequencing may be useful because CMA does not detect single-gene (Mendelian) disorders. If exome sequencing is pursued, appropriate pretest and posttest genetic counseling by a provider who is experienced in the complexities of genomic sequencing is recommended.
International Society for Prenatal Diagnosis, Society for Maternal Fetal Medicine, Perinatal Quality Foundation Joint Position Statement from the International Society for Prenatal Diagnosis (ISPD), the Society for Maternal Fetal Medicine (SMFM), and the Perinatal Quality Foundation (PQF) on the use of genome-wide sequencing for fetal diagnosis.
Thrombocytopenia-absent radius syndrome is often caused by a deletion, which may be identified by CMA on one allele, and a sequence variant that may be detected by sequencing on the second allele. After appropriate counseling, cell-free DNA screening is an option for patients who decline diagnostic evaluation if a common aneuploidy is suspected.
Pregnancy and Delivery Management
A detailed ultrasound examination should be performed and should include assessment of all of the long bones and the hands. The fetal heart should be evaluated carefully, and a fetal echocardiogram should be considered given the association with syndromic disorders. Referrals to pediatric orthopedics or other subspecialty services should be based on additional sonographic findings. Pregnancy termination is an option that should be discussed with all patients in whom a fetal anomaly is detected. Shared patient decision-making requires a thorough evaluation and multidisciplinary counseling regarding prognosis. The specific finding of a radial ray malformation generally does not affect delivery management, although delivery at a tertiary care center with pediatric genetics and orthopedic surgery consultation should be considered, as appropriate for the clinical findings. After delivery, the infant should be referred to a specialist for potential reconstructive surgery. Radial ray malformations that are associated with other system anomalies or syndromes are managed based on the severity of the findings.
Prognosis
The prognosis in isolated cases includes functional limitations that result from the skeletal deformity. Reconstructive surgery may improve the mobility of the affected limb. Prognosis also depends on the severity of associated abnormalities, underlying causes, and potential association with genetic syndromes. Isolated findings are usually sporadic, with a low recurrence risk. Recurrence of syndromic cases depends on the underlying cause.
Summary
Radial ray malformations are most commonly an isolated finding and can be unilateral or bilateral. Careful examination of the entire fetus will help determine whether there are associated anomalies. A genetic evaluation is recommended to determine the presence of an underlying syndrome. Prognosis depends on the severity of associated abnormalities and the presence of a genetic abnormality. Reconstructive surgery may improve limb mobility.
References
James M.A.
McCarroll Jr., H.R.
Manske P.R.
The spectrum of radial longitudinal deficiency: a modified classification.
International Society for Prenatal Diagnosis, Society for Maternal Fetal Medicine, Perinatal Quality Foundation
Joint Position Statement from the International Society for Prenatal Diagnosis (ISPD), the Society for Maternal Fetal Medicine (SMFM), and the Perinatal Quality Foundation (PQF) on the use of genome-wide sequencing for fetal diagnosis.
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