Mosaic Trisomy 5: Prenatal Genetic Diagnosis and Outcomes of a New Case

Chromosomal mosaicism is defined as the presence of two or more different cell lines in an organism that originate from the same embryo. Trisomy of chromosome 5 is one of the most severe forms of autosomal trisomy and only seven cases of mosaic trisomy 5 have been reported to date. Mosaicism at prenatal level constitutes a challenge in genetic counseling, particularly in the case of mosaic trisomy 5, due to its low incidence. We report the case of a girl with a prenatal diagnosis of mosaic trisomy 5. The pre- and postnatal genetic tests (noninvasive prenatal testing, array comparative genomic hybridization, karyotype in amniotic fluid cells, karyotype in peripheral blood, and uniparental disomy analysis) revealed the fetal chromosomal status and indicated etiology giving rise to the mosaicism, suggesting a prezygotic meiotic error corrected through late trisomic rescue in the zygote.

A prenatal diagnosis of mosaic trisomy 5 reveals a postnatal complete uniparental disomy of chromosome 5 with multiple congenital anomalies

Mosaic trisomy 5 is a very rare condition in liveborns, with few cases reported in the last four decades. There are some reports of prenatally diagnosed mosaic trisomy 5 resulting in phenotypically normal offspring, suggesting a low level of mosaicism, but there are also reports associated with multiple congenital anomalies, cardiovascular malformations, and intrauterine growth restriction. We report an infant male diagnosed with mosaic trisomy 5 (5/15 cells) via amniocentesis. The patient was subsequently found to have uniparental disomy 5 (UPD5) by postnatal chromosome microarray, but high-resolution chromosome analysis on peripheral blood did not identify trisomy 5. Dysmorphic features included a tall forehead with low anterior hairline, hypertelorism, low-set ears, and a prominent nose and midface. Other anomalies included bilateral bifid thumbs, hypospadias, a perineal fistula, unilateral multicystic kidney, and decreased subcutaneous fat with loose skin. He had complex congenital heart disease consisting of ventricular and atrial septal defects and polyvalvular defects. The patient died at age one after a prolonged admission. We add this case to the literature with the added benefit of data from a postnatal microarray, which was not available in other cases, to broaden the phenotype of mosaic trisomy 5 and UPD5.With the current available technology, we stress the importance of postnatal genetic testing to confirm prenatal cytogenetic findings in order to further define such phenotypes. This will provide the most accurate information and counseling to affected families.

Diffuse-type tenosynovial giant cell tumor with t(1;17)(p13;p13) and trisomy 5

Diffuse-type tenosynovial giant cell tumor (TSGCT) is a locally aggressive neoplasm that primarily affects the synovium and tendon sheath in young adults. Rearrangement of chromosome band 1p13 is now considered a characteristic genetic feature of TSGCT, with the most frequent chromosomal alteration t(1;2)(p13;q37). Here, we describe a unique cytogenetic finding of diffuse-type TSGCT arising in the ankle of an 18-year-old woman. Magnetic resonance imaging demonstrated an ill-defined juxta-articular mass with decreased signal intensity on both T1- and T2-weighted images. Contrast-enhanced T1-weighted images showed intense enhancement of the mass. Open complete resection was performed. Histologically, the tumor was composed of mononuclear cells admixed with multi-nucleated osteoclast-like giant cells, foam cells, siderophages and inflammatory cells. Cytogenetic analysis revealed a reciprocal translocation involving chromosomes 1 and 17, concomitant with a few other numerical and structural alterations. In addition, trisomy 5 as the sole anomaly was identified in two metaphase cells. To the best of our knowledge, this is the first report of this neoplasm with t(1;17)(p13;p13).