Three cases of tetrasomy 9p

Abstract

We report three cases of tetrasomy 9p, two of which were confirmed prenatally. All three had characteristic findings on ultrasound and at birth. We also present a review of the literature, which suggests that a recognizable phenotype for this condition is emerging. Common findings on prenatal ultrasound include intrauterine growth restriction, ventriculomegaly, cleft lip or palate, and renal anomalies. These findings can provide a clue toward the prenatal diagnosis of this condition. There is also a clearly recognizable phenotype at birth. Facial characteristics include hypertelorism, broad nasal bridge/bulbous or beaked nose, cleft lip/palate, ear anomalies, and micrognathia. The exact extent of the isochromosome does not seem to predict severity, but mosaic cases are less severe, or at least have a greater probability of survival.

Congenital diaphragmatic hernia in a patient with tetrasomy 9p

“…Isochromosomes predominantly originate through maternal meiosis type II nondisjunction, followed by a rearrangement or centromeric misdivision, leading to duplication of the short arm and loss of the long arm [8]. Isochromosomes derived from chromosome 9 have been reported and may be grouped in 3 types: isochromosomes with a breakpoint at p10 with no portion of the long arm, isochromosomes with a small amount of the heterochromic region of 9q extending to 9q12 or 9q13, and isochromosomes with a large portion of the long arm of chromosome 9 extending to 9q21 or q22 [9]. Some patients with an extra isochromosome 9p have the abnormal cell line in all tissues investigated, but many display tissue mosaicism.…”

Tetrasomy 9p Mosaicism Associated with a Normal Phenotype

“…A wide variation in phenotype has been reported in the literature in association with tetrasomy 9p, ranging from mild developmental delay [9] to lethal malformations [3] . It has been suggested that clinical fi ndings may be infl uenced by 3 cytogenetic parameters, i.e.…”

“…Reports in the literature of tetrasomy 9p, numbering about 32 and including both mosaic and nonmosaic cases, describe a recognizable syndrome with a characteristic facial appearance, hypertelorism (72%), a broad nasal root (69%), cleft lip and palate (78%), ear anomalies (88%) and micrognathia [3] . Other clinical features include developmental delay, reported in 94% of cases, central ner- vous system anomaly (89%), limb defects (88%), congenital heart disease (62%) and postnatal growth failure (71%) [3][4][5][6][7][8] .…”

“…Other clinical features include developmental delay, reported in 94% of cases, central ner- vous system anomaly (89%), limb defects (88%), congenital heart disease (62%) and postnatal growth failure (71%) [3][4][5][6][7][8] .…”

“…Because of the previous pregnancy loss after cordocentesis, the parents were unwilling to undergo this procedure again. Tetrasomy 9p is associated with fi ndings on prenatal ultrasound such as intrauterine growth restriction, ventriculomegaly, cleft lip or palate and renal anomalies [3] . The absence of these anomalies also provided reassurance that all appeared to be well with the pregnancy.…”