Further observations of ocular pathology in trisomy 9

[Mosaic trisomy 9: report of a new case with a long-term survival]

INTRODUCTION

Trisomy 9 is an uncommon chromosome abnormality that may be seen in a mosaic or non-mosaic state.

OBJECTIVE

To better define the phenotype and prognosis of this disorder we report a new case of mosaic trisomy 9 with a long-term survival.

CLINICAL REPORT

We present the case of a female patient, born from the first pregnancy of a healthy couple. Fetal ultrasounds disclosed intrauterine growth retardation and oligohydramnios. Cesarean section was performed in the 34th week. Birth weight was 1,478 g. Neonatal examination showed: dolichocephaly; hypotelorism, microphthalmia, short palpebral fissures; broad-based nose with bulbous tip; micrognathia; low-set malformed ears; abnormal hands and feet; no other malformations. The initial karyotype determination was normal (46,XX). At 17 months of age, a second karyotype was requested because the patient developed severe psychomotor retardation. Chromosome analysis showed mosaic trisomy 9 (46,XX/47,XX, + 9). Six months later, a single upper central incisor was noted. To our knowledge, this feature has not been reported previously in the trisomy 9. The patient is now 4 years old. She shows severe psychomotor retardation, but no other complications.

COMMENTS

It is important to be aware of the possibility that mosaicism may exist in a patient with normal blood karyotype and abnormal phenotype. We conclude that a great number of cells is needed in order to obtain a correct karyotype diagnosis. Correct diagnosis is essential to define the prognosis and provide accurate genetic counselling.

Prenatal diagnosis of tetrasomy 9p in a 19-week-old fetus with Dandy-Walker malformation: a case report

OBJECTIVE

The presentation of sonographic and perinatal findings of tetrasomy 9p.

METHODS AND RESULTS

Chorionic villus sampling and amniocentesis were performed at 19 weeks of gestation because of the sonographic findings of Dandy-Walker malformation with bilateral ventriculomegaly. Cytogenetic analysis showed 47,XX,+i psu dic(9)(pter->q12::q12>-pter). The pregnancy was terminated at 20 weeks of gestation at the request of the parents. At post-mortem examination, the presumed hypoplasia of the vermis could not be confirmed for technical reasons. No other pathological findings were seen.

CONCLUSION

From our experience and from the literature, we conclude that Dandy-Walker malformation is an important finding in tetrasomy 9p. Chromosomal studies should be carried out in fetuses with sonographically detected Dandy-Walker malformation, even in the absence of other abnormalities.

Prenatal diagnosis of the Dandy-Walker malformation and ventriculomegaly associated with partial trisomy 9p and distal 12p deletion

OBJECTIVES

To present the prenatal diagnosis and perinatal findings of partial trisomy 9p and distal 12p deletion.

METHODS AND RESULTS

Amniocentesis was performed at 17 gestational weeks due to a balanced reciprocal translocation t(9;12)(p11.2;p13.3) in the mother. The father's karyotype was normal. The family had a 5-year-old daughter with a Dandy-Walker malformation and a trisomy 9p syndrome. Cytogenetic analysis of the cultured amniotic fluid cells revealed a 46,XY,der(12)t(9;12)(p11.2;p13.3)mat karyotype with partial monosomy 12p(12pter-->p13.3) and partial trisomy 9p(9pter-->p11.2). Sonographic examination of the fetal brain and skull showed bilateral ventriculomegaly, brachycephaly and a Dandy-Walker malformation with an enlarged cisterna magna and absence of the cerebellar vermis. The pregnancy was terminated subsequently. At autopsy, the proband manifested agenesis of the cerebellar vermis and a typical trisomy 9p phenotype.

CONCLUSION

Fetuses with partial trisomy 9p(9pter-->p11.2) may present a Dandy-Walker malformation and ventriculomegaly on prenatal ultrasound in the second trimester. A dosage effect of genes located on 9pter-->p11.2 may be associated with the abnormal development of the central nervous system in patients with partial or complete trisomy 9.

Trisomy 9: review and report of two new cases

Trisomy 9 is a relatively uncommon chromosome abnormality that may sometimes be seen in the nonmosaic state. We reviewed 23 mosaic and 15 nonmosaic cases of trisomy 9, including 2 new cases, in order to better define the prognosis and phenotype of this disorder. A recognizable trisomy 9 phenotype was identified and included a "bulbous" nose, microphthalmia, and dislocated limbs. Other nonspecific anomalies involving various organ systems were also common. With one exception, all survivors had severe mental impairment. Mosaicism for trisomy 9 predicted longer survival, but the degree of mosaicism in lymphocytes or fibroblasts did not predict survival or degree of impairment. Parental chromosome variations were not uncommon. In contrast to prior reports, no specific prognostic finding was identified. A meiotic origin with loss of a trisomic cell line in mosaic cases is suggested.

Trisomy 9 mosaicism in two girls with multiple congenital malformations and mental retardation

Two girls with mosaicism for an extra chromosome 9 are reported. Clinical findings included growth and mental retardation, facial dysmorphism, delayed ossification, single flexion crease, gastro-oesophageal reflux in one girl, and ventricular and atrial septal defects in the other patient. These findings are compared to the other previously reported cases of trisomy 9 mosaicism.

Prenatal diagnosis of trisomy 9 mosaic presenting as a case of Dandy-Walker malformation

Trisomy 9 syndrome is a rare chromosomal anomaly associated with specific patterns of multisystem dysmorphism and occasional central nervous system (CNS) malformations, the most common being the Dandy-Walker malformation. Milder anomalies are usually seen with trisomy 9 mosaicism. We report what we believe to be the first case of a baby with an isolated Dandy-Walker malformation which was diagnosed prenatally and was subsequently found to have a trisomy 9 mosaic syndrome.