Prenatal diagnosis and findings of tetrasomy 9p

Abstract

Tetrasomy 9p is a rare condition initially reported by Ghymers et al. Reported cases are a mix of prenatal and neonatal/pediatric cases in non-mosaic and mosaic cases. We report on the common mechanism leading to this form of chromosome abnormality, the various types of tetrasomy 9p as well as the prenatal sonographic and laboratory presentation of our case and previously reported cases with mosaic and non-mosaic tetrasomy 9p. From these reported cases, a recognizable syndrome is emerging. Multiple fetal abnormalities amenable to ultrasound diagnosis are likely to be present. However, neither ultrasound study alone nor the first-trimester screen for the common aneuploidies can suggest the correct diagnosis. Chromosome study of more than a single tissue is necessary in order to establish the correct diagnosis and to differentiate between mosaic and non-mosaic tetrasomy 9p cases.

A systematic clinical review of prenatally diagnosed tetrasomy 9p

“…In 10 cases of tetrasomy 9p, the abnormal ultrasound findings were reported in the second trimester. The most common fetal anomalies were CNS abnormalities (8/10) [5,7,15,32,33,37,39,45], genitourinary tract anomalies (6/10) [5,32,37,39,45], skeletal/limb abnormalities (5/10) (our case) and facial dysmorphism (5/10) (our case [5,7,39, 45]). Additional anomalies were discovered in less than five cases.…”

“…Pregnancy outcome following PND of tetrasomy 9p were termination of pregnancy in 14/22 cases (our case [4,5,7,15,32,34,37,39,40,46,52]), neonatal death (3/22)…”

“…Altogether, most of the reported cases of tetrasomy 9p were associated with severe congenital abnormalities. The most common prenatally detected features of tetrasomy 9p were central nervous system (CNS) abnormalities (13/22) (our case [3,5,7,15,32,33,37, 38, 39, 40,45,47]), limb/ skeletal malformations (11/22) (our case [1,5,7,32,38, 39, 40,45,47,51)], intrauterine growth retardation (IUGR) (10/22) [1,3, 4, 5,7,33, 38,39,46], cleft lip and/or palate (10/22) (our case [1,5, 32,38,39,45, 46, 47)], and facial dysmorphism (8/22) (our case [5,7,39,40,45,46)]. All the details and less common anomalies are presented in Tables 1 and 2.…”

“…This wide variability of clinical features in fetuses with tetrasomy 9p (Tables 2 and 3) might be explained by the difference of a mosaic vs . non-mosaic forms, the level of mosaicism, a limitation of chromosomal anomaly to certain tissues, and the size of the isochromosome 9p and Hsa9 genes presented in four copies [5,7,34,36,44].…”

“…Especially in the later years, the detection rate of tetrasomy 9p increased with better fetal monitoring and more accessible prenatal diagnostics. Fourteen cases were reported in last 3 years [4,5,6,7], detected using microarrays in comparison with 53 cases reported from 1973 to 2015 using GTG banding and/or fluorescent in situ hybridization (FISH), analysis [1,2,3,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52].…”