Sirenomelia. Pathological features, antenatal ultrasonographic clues, and a review of current embryogenic theories.
We aimed to discuss the prenatal diagnosis and pathological features of sirenomelia, and to review current embryogenic theories. We observed two sirenomelic fetuses that were at the 19th and 16th gestational week respectively. In the former, transvaginal ultrasound revealed severe oligohydramnios and internal abortion, whereas bilateral renal agenesis, absence of a normally tapered lumbosacral spine, and a single, dysmorphic lower limb were detected in the latter. In both cases, X-rays and autoptic examination allowed categorization on the basis of the skeletal deformity. Subtotal sacrococcygeal agenesis was present in both cases. Agenesis of the urinary apparatus and external genitalia and anorectal atresia were also found. Classification of sirenomelia separately from caudal regression syndrome is still debated. Recent advances in the understanding of axial mesoderm patterning during early embryonic development suggest that sirenomelia represents the most severe end of the caudal regression spectrum. Third-trimester ultrasonographic diagnosis is usually impaired by severe oligohydramnios related to bilateral renal agenesis, whereas during the early second trimester the amount of amniotic fluid may be sufficient to allow diagnosis. Early antenatal sonographic diagnosis is important in view of the dismal prognosis, and allows for earlier, less traumatic termination of pregnancy. (+info)
A minimalist approach to gene mapping: locating the gene for acheiropodia, by homozygosity analysis.
Acheiropodia is an autosomal recessive disease that results in hemimelia (lack of formation of the distal extremities). We performed a complete genome screen of seven members of an extended pedigree that included three siblings with acheiropodia. Homozygosity mapping was used to identify regions most likely to harbor the gene for acheiropodia in this pedigree. In these two key regions (14p and 7q), further genotyping of one additional affected member of this pedigree plus seven additional unaffected siblings provided evidence, through linkage analysis, that the 7q36 region contains the acheiropodia gene. In this region, a maximum two-point LOD score of 3.81 (4.2 with multipoint analysis) was achieved, and a homozygous haplotype spanning a region of 11.7 cM was seen in all affected in this pedigree. Finally, genotypic analysis of two additional cases of acheiropodia with no known relation to the other samples revealed homozygous sharing of a portion of the same haplotype on 7q36, which reduces the chromosomal location of the acheiropodia gene to an 8.6-cM region. Localization of this gene, at the screening level, by use of data from only three affected subjects, provides an example of how certain genes may be mapped by use of a minimal number of affected cases. (+info)
Beyond re-membering: phantom sensations of congenitally absent limbs.
Phantom limbs are traditionally conceptualized as the phenomenal persistence of a body part after deafferentation. Previous clinical observations of subjects with phantoms of congenitally absent limbs are not compatible with this view, but, in the absence of experimental work, the neural basis of such "aplasic phantoms" has remained enigmatic. In this paper, we report a series of behavioral, imaging, and neurophysiological experiments with a university-educated woman born without forearms and legs, who experiences vivid phantom sensations of all four limbs. Visuokinesthetic integration of tachistoscopically presented drawings of hands and feet indicated an intact somatic representation of these body parts. Functional magnetic resonance imaging of phantom hand movements showed no activation of primary sensorimotor areas, but of premotor and parietal cortex bilaterally. Movements of the existing upper arms produced activation expanding into the hand territories deprived of afferences and efferences. Transcranial magnetic stimulation of the sensorimotor cortex consistently elicited phantom sensations in the contralateral fingers and hand. In addition, premotor and parietal stimulation evoked similar phantom sensations, albeit in the absence of motor evoked potentials in the stump. These data indicate that body parts that have never been physically developed can be represented in sensory and motor cortical areas. Both genetic and epigenetic factors, such as the habitual observation of other people moving their limbs, may contribute to the conscious experience of aplasic phantoms. (+info)
Tibial hemimelia, meningocele, and abdominal hernia in Shorthorn cattle.
Six genetically related Shorthorn calves were affected with the tibial hemimelia syndrome. The lesions included bilaterally malformed or absent tibia and abdominal hernia in all animals, a long shaggy haircoat, retained testicles in males, and meningocele in three animals. The malformations were similar to those described previously in Galloway calves. Pedigree analysis demonstrated a mechanism by which a recessive allele in a homozygous state could be responsible for the disorder. The condition in these calves was considered the result of a recurrence of a genetic mutation affecting a putative hemimelia locus. (+info)
Caudal regression syndrome versus sirenomelia: a case report.
We describe a newborn with clinical features of sirenomelia including fused lower limbs with medial position, absence of fibula, anal atresia, bilateral renal agenesis, and a single large umbilical artery. Recent literature describing the etiology of sirenomelia and relationship to caudal regression syndrome is reviewed. (+info)
Caudal Regression Syndrome in twin pregnancy with type II diabetes.
Caudal Regression Syndrome (CRS) is a rare fetal complication of diabetic pregnancy, which can result in long-term neurological, urologic, and orthopedic complications. Although the exact teratogenic mechanism is not known, hyperglycemia appears to play a crucial role as a teratogen, and therefore, stringent control of diabetes preconceptually and in early pregnancy is presumed to reduce the risk of occurrence. We report an unusual case of CRS affecting only one of a set of monozygotic twins, suggesting that as yet, unidentified factors other than hyperglycemia are included in its causation. (+info)
Sirenomelia sequence: first-trimester diagnosis with both two- and three-dimensional sonography.
OBJECTIVE: To describe the sonographic findings of sirenomelia during the first trimester on both two-dimensional sonography with color Doppler imaging and three-dimensional sonography. METHODS: Two cases of sirenomelia in primiparous patients with histories of infertility are described. The diagnosis was made on the basis of two-dimensional sonography, and three-dimensional sonography was used to further characterize the findings. RESULTS: Both fetuses had size-date discrepancies, increased nuchal translucency, large intra-abdominal vessels, and 2-vessel umbilical cords. Both pregnancies were terminated by dilation and curettage after the patients viewed the three-dimensional pictures of the fetuses. CONCLUSIONS: During the first trimester of pregnancy, rare and lethal anomalies can be diagnosed with a high degree of confidence if a thorough, age-dependent anatomic survey of the fetus is performed. (+info)
Radiological findings in three cases of paraxial radial hemimelia in goats.
Hemimelia is a congenital abnormality characterized by the absence of a portion of the normal structures in a limb. Hemimelia is classified as transversal and paraxial and is related to genetical and environmental factors. This article shows the radiological findings observed in three different cases of paraxial hemimelia occurred in goats (radial agenesia, absence of the portion of the distal epiphysis of the radius and anomalous radius with ulnar hypoplasia). Possible causes related to these abnormalities are discussed. (+info)