Trisomy 22 with holoprosencephaly: a clinicopathologic study

Syndromes associated with holoprosencephaly

Holoprosencephaly (HPE) is partial or complete failure of the forebrain to divide into hemispheres and can be an isolated finding or associated with a syndrome. Most cases of HPE are associated with a syndrome and roughly 40%-60% of fetuses with HPE have trisomy 13 which is the most common etiology of HPE. Other syndromes associated with HPE include additional aneuploidies like trisomy 18 and single gene disorders such as Smith-Lemli-Opitz syndrome. There are a number of syndromes such as pseudotrisomy 13 which do not have a known molecular etiology; therefore, this review has two parts: syndromes with a molecular diagnosis and syndromes where the etiology is yet to be found. As most HPE is syndromic, this review provides a comprehensive list and description of syndromes associated with HPE that may be used as a differential diagnosis and starting point for evaluating individuals with HPE.

Antenatal Detection of Trisomy 22

Trisomy 22 (47, XX, +22), a rare chromosomal defect, was detected antenatally by chromosome analysis of the amniotic fluid after an obstetric ultrasound examination revealed multiple anomalies. The ultrasound findings included intrauterine growth retardation, holoprosencephaly, cleft lip, cardiac anomalies, decreased amniotic fluid level, and an abnormally thickened nuchal fold. Postnatal examination and autopsy confirmed the ultrasound findings.

Discordant semilobar holoprosencephaly in monozygotic twins with de novo inv dup(15) marker chromosome and de novo mutation on SHH gene

We present a 30-year-old woman with a twin pregnancy, 1 fetus displaying a small head circumference, semilobar holoprosencephaly, and cleft lip as detected by ultrasound at 23 weeks of gestation. Fetal magnetic resonance imaging confirmed the diagnosis of semilobar holoprosencephaly. The other twin, however, had an appropriate fetal growth, devoid of any major structural anomalies. Karyotyping by G-banding of amniocentesis specimens in both fetuses showed 47,XY,+mar. Fluorescence in situ hybridization showed in the marker chromosome positive dicentric signals for the chromosome 15 centromere-specific alpha satellite DNA probe (D15Z1) and negative signals for the SNRPN probe (15q11-13), thus establishing a cytogenetic diagnosis of 47,XX,+mar.ish idic(15)(q11-q13)(D15Z1++,SNRPN-) for both fetuses. The parental karyotypes were normal. The fetuses, therefore, had a de novo inv dup(15) marker chromosome without involvement of the Prader-Willi region. Short tandem repeat markers (total 15 markers) confirmed that the fetuses were monozygotic twins. Short tandem repeat markers at the 15q region (total 6 markers) excluded the possibility of uniparental disomy (15) mat or uniparental disomy (15) pat. Molecular study in both fetuses of TGIF, SHH, SIX3, and ZIC2 genes revealed a heterozygous 1085 C > T (Ser 362 Leu) on the SHH gene, but a homozygous 1085 C > C (Ser 362 Ser) for both parents on the SHH gene. The couple decided to terminate the pregnancy at 26 weeks of gestation. To our knowledge, this is the first report of semilobar holoprosencephaly with inv dup(15) marker chromosome and missense SHH gene mutation 1085 C > T (Ser 362 Leu).

Fryns syndrome phenotype and trisomy 22

Trisomy 22 was detected in a 32-week-old fetus born to an overweight mother with hypertension. Severe intrauterine growth retardation was associated with phenotypic manifestations of Fryns syndrome: diaphragmatic hernia, facial defects, and nail hypoplasia with short distal fifth phalanges. This is the second report of congenital diaphragmatic hernia in trisomy 22. This case demonstrates the importance of karyotyping malformed fetuses or newborns, even if a nonchromosome syndrome seems identifiable on clinical grounds. To date, at least 10 cases of Fryns syndrome have been reported without chromosome analysis.

Goldenhar sequence and mosaic trisomy 22

We describe a term infant with facioauriculo-vertebral "dysplasia" (Goldenhar sequence), hypertelorism, and mosaic trisomy 22: peripheral blood, 46, XY/47, XY, + 22 (72%/28%); skin fibroblasts, 47, XY, + 22 (100%). This is the second report of Goldenhar anomaly with epibulbar dermoids in a liveborn infant with aneuploidy. Hypertelorism is rare in Goldenhar sequence, but typical of trisomy 22. We recommend chromosome analysis in all patients with Goldenhar sequence. Those with hypertelorism may be more likely to have aneuploidy as well.

Clinical and molecular studies in full trisomy 22: further delineation of the phenotype and review of the literature

Trisomy 22 is commonly found among spontaneous abortions, second in frequency of occurrence only to trisomy 16. Most earlier reports of surviving trisomy 22 cases in the literature are thought to represent the product of unbalanced 11;22 translocations or the result of undetected mosaicism, since this condition is thought to manifest early embryonic or fetal lethality. We present two strikingly similar cases of non-mosaic trisomy 22 surviving to late gestation. In this paper we emphasize the unique phenotype of this trisomy which included intrauterine growth retardation, microcephaly, broad flat nasal bridge with epicanthal folds and ocular hypertelorism, microtia, variable cleft palate, webbed neck, congenital heart defects involving anomalous great vessels, anorectal and renal anomalies, and hypoplastic distal digits with thumb anomalies. We also explore why some cases survive to late gestation. Confined placental mosaicism, a frequent finding in other lethal trisomies, has been ruled out in one of the cases. Molecular studies done to assess the parental origin of the extra chromosome in the other case showed that the non-disjunction originated during maternal meiosis II. Parental origin of the extra chromosome does not seem to play a role in late survival for trisomy 22.

Hydrocephalus in an infant with trisomy 22

We present an infant with true trisomy 22. Mosaicism is ruled out by the finding of a 47,XX, +22 karyotype in all cells analysed originating from two embryonic germ layers. The physical findings are consistent with the previously noted features including developmental delay, ear abnormalities, micrognathia, clefting, and congenital heart disease. The patient is the first described with macrocephaly and hydrocephalus and the second with holoprosencephaly.

Confirmation of trisomy 22 in two cases using chromosome painting: comparison with t(11;22)

We present a nonmosaic case of trisomy 22 in a liveborn, abnormal infant and a second case of a fetus who died in utero. Both have been verified cytogenetically and confirmed by in situ hybridisation with a centromeric alphoid probe and chromosome painting. The accuracy of the combined cytogenetic and molecular cytogenetic approaches in the karyotype determination is highlighted by comparison with a case showing partial translocation of chromosome 22 in t(11;22) (q23;q11).

Trisomy 22 and facioauriculovertebral (Goldenhar) sequence

We report on an infant girl born with complete trisomy 22 and left hemifacial microsomia, ear anomaly, and limbal and epibulbar complex choristoma. Trisomy 22 was confirmed by prometaphase chromosome analysis and in situ hybridization. This patient extends the list of chromosome abnormalities associated with apparent Golenhar sequence and emphasizes the importance of chromosome analysis in the investigation of patients with this condition. A detailed ophthalmopathological investigation is reported.

Trisomy 22 confirmed by fluorescent in situ hybridization

We report on a newborn girl with multiple congenital anomalies, whose G-banded chromosome analysis showed complete trisomy 22. Chromosome painting using a whole-chromosome painting probe for chromosome 22 confirmed that neither chromosome 22 was involved in a cryptic translocation.

Trisomy 22 with congenital diaphragmatic hernia and absence of corpus callosum in a liveborn premature infant

We report on a liveborn premature male with trisomy 22 who had multiple congenital anomalies, including congenital diaphragmatic hernia and absence of corpus callosum. He died of pulmonary hypoplasia associated with diaphragmatic hernia within 12 hours of age. Chromosome analysis by multiple banding techniques based on lymphocyte culture confirmed that he had trisomy 22. This may be the first report of congenital diaphragmatic hernia and isolated absence of corpus callosum associated with trisomy 22.