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Background: To date, only twenty-one cases diagnosed postnatally with mosaic trisomy 12 have been reported. The most frequent phenotypic manifestations are developmental delay, dysmorphic facial features, congenital heart defects, digital alterations, and pigmentary disorders. In the present report, detailed clinical and genetic profiles of three unrelated new patients with mosaic trisomy 12 are described and compared with previously reported cases., Case Presentation: In the present report, we include the clinical, cytogenetic, and molecular description of three Mexican patients diagnosed postnatally with mosaic trisomy 12. At phenotypic level, the three patients present with developmental delay, dysmorphic facial features, congenital heart defects and skin pigmentary anomalies. Particularly, patient 1 showed unique eye alterations as bilateral distichiasis, triple rows of upper lashes, and digital abnormalities. In patient 2 redundant skin, severe hearing loss, and hypotonia were observed, and patient 3 presented with hypertelorism and telecanthus. Hyperpigmentation with disseminated pigmentary anomalies is a common trait in all of them. The cytogenetic study was carried out under the strict criteria of analysis, screening 50-100 metaphases from three different tissues, showing trisomy 12 mosaicism in at least one of the three different tissues analyzed. With SNParray, the presence of low-level mosaic copy number variants not previously detected by cytogenetics, and uniparental disomy of chromosome 12, was excluded. STR markers allowed to confirm the absence of uniparental disomy as well as to know the parental origin of supernumerary chromosome 12., Conclusions: The detailed clinical, cytogenetic, and molecular description of these three new patients, contributes with relevant information to delineate more accurately a group of patients that show a heterogeneous phenotype, although sharing the same chromosomal alteration. The possibility of detecting mosaic trisomy 12 is directly associated with the sensitivity of the methodology applied to reveal the low-level chromosomal mosaicism, as well as with the possibility to perform the analysis in a suitable tissue., (© 2022. The Author(s).)

Mosaic variegated aneuploidy syndrome (MVA) is a rare autosomal recessive disorder characterized by random chromosome gains and losses. Mutations in BUB1B and CEP57 genes have been involved in MVA. Here we report on a male child with MVA due to c.915_925dupCAATGTTCAGC mutation in the CEP57 gene. Our patient was homozygous for this mutation and he is the first case with rhizomelic shortening of both the upper and lower limbs and mild respiratory insufficiency due to a narrow thorax. It is also the second MVA Mexican family reported with this mutation that lives in the northwestern region of Mexico, suggesting a "local founding effect". Additional cases are needed to better understand the MVA genotype-phenotype relationship., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)