Prenatal Diagnosis of a Case of Partial Monosomy^|^frasl;Monosomy 13 Mosaicism: 46,XX,r(13)(p11q33)^|^frasl;45,XX,-13 Suspected by Nuchal Fold Translucency Increasing

Abstract

Summary:Large numbers of patients with deletions of the long arm of chromosome 13 have been described. However, only a few instances have been reported of monosomy 13/r(13) mosaicism. A 31-year-old Japanese woman underwent an ultrasound tomographic screening, which detected a fetus with a nuchal translucency (NT) of >5.8mm, indicating an increased risk of fetal chromosomal abnormality. An amniocentesis (AC) was performed, and the karyotype was 46,XX,r (13)(p11q33)[18]/45XX [12]. Ultrasound showed echogenic skin edema. Phenotype of the fetus after delivery revealed some anomalies, including hyponasal bridge, hypertelorism, ambiguous genitalia with huge clitoris, low-set ear, neck edema and webbing.Deletion of the long arm of chromosome 13 is associated with a wide spectrum of abnormalities, including retinoblastoma, mental and growth retardation, brain malformations, heart defects, distal limb deformities, and digestive, urogenital, and other abnormalities. The present case, however, had anomalies which were too faint to be detected by ultrasound tomography. Prenatal diagnosis of deletion 13q syndrome is rare. A number of reports have documented an association between increased NT and chromosomal defects. Ultrasound did not identify any major anomaly in this case, however amniocentesis was able to detect this rare abnormality.

Prenatal Sonographic Features of Rare Chromosome 13 Aberrations

“…Similar abnormalities reported by Kataoka et al presented a fetus with mosaic ring chromosome 13 with monosomy 13 (46,XX,r (13)(p11q33)/45,XX,-13) with slightly sloping forehead, hyponasal bridge, hypertelorism, ambiguous genitalia, low-set ear, neck edema, and webbing. 5 Figure 3 Hypospadias with the bifid scrotum in the fetus with a deletion 13q31.1q34 (case number 2 in Table 1).…”

“…2 Rare aberrations of chromosome 13 may have features other than observed in chromosome 13 trisomy. [3][4][5][6] Screening and diagnostic tests are used to diagnose chromosomal abnormalities in the fetus. Screening tests calculate the risk of the most common trisomies, including trisomy 13 in the fetus.…”