Prenatal diagnosis of Jacobsen syndrome. B.R. DuPont¹, G.A. Stapleton¹, S. Chapman². 1) Greenwood Genetics Ctr, Greenwood, SC; 2) Center for Women's Medicine, Greenville Memorial Hospital System Greenville, SC.
   Jacobsen syndrome is a contiguous gene deletion syndrome caused by the deletion of chromosome 11q23 to qter. Persons with this deletion exhibit a variety of characteristics, including moderate to severe psychomotor retardation, trigonocephaly, heart defects, hypertelorism, low-set dysmorphic ears, and small stature. Prenatal diagnosis of Jacobsen syndrome has been previously reported for only a single case (McClelland et al., 1998). In this case report, the only abnormality detected at ultrasound was nuchal thickening. Examination after birth revealed other findings consistent with Jacobsen syndrome.
   Our patient, a 37 year old G3P2 was referred at 22 weeks gestation for a genetic amniocentesis because of advanced maternal age and increased nuchal thickness on routine ultrasound. Targeted ultrasound at amniocentesis revealed multiple congenital anomalies including nuchal thickening from the base of the skull to the upper thoracic spine, a hypoplastic left heart, an irregularity of the lumbosacral area of the spine, bilateral clubbed feet, a widened iliac angle, and low-set ears. Fetal echocardiogram confirmed the heart defect. FISH results for aneuploidy were normal. The complete karyotype of the fetus revealed a terminal deletion of chromosome 11q23. The pregnancy was terminated at 23 weeks. The family declined postmortem examination. The parents' karyotypes were normal and neither expressed the folate-sensitive fragile site found at 11q23.3, FRA11B.To our knowledge, prenatal diagnosis of Jacobsen syndrome has previously been reported in only one other case.