The spectrum of cytogenetics and clinical profile in Robertsonian translocations: An experience of two decades from tertiary referral center in India.

BACKGROUND

Robertsonian translocations (Rob-t) are the most common structural chromosomal abnormalities observed in humans. Cytogenetic analysis remains essential to identify these abnormalities which cannot be identified by currently used DNA-based tests. This study describes the cytogenetic profile and clinical presentations of Rob-t.

METHODS

This was a retrospective observational study of patients with Rob-t who underwent cytogenetic analysis at a tertiary-care center in south India from 2001 to 2019.

RESULTS

Rob-t were observed in 88/12,227(0.72%) patients tested including 4/1425 (0.28%) prenatal samples. There were 21 (0.09%) adults and 63 (0.58%) children (M:F = 1.27:1). With 10 types of Rob-t, eight (72.7%) heterologous and two homologous (27.3%). Thirty(34%) were balanced and 58(66%) unbalanced (associated with trisomy). All 21 adults had balanced Rob-t and had recurrent pregnancy loss, infertility/oligospermia, premature ovarian failure or were carrier parents. All unbalanced Rob-t were observed in children with trisomy 21(98.2%) or trisomy 13(1.8%). The der(14;21), der(21;21) and the der(13;14) accounted for 32(36.4%), 22(25%) and 17(19.3%), respectively and the other Rob-t for <6% each; 16(18.2%) der(13;14) were balanced.One child had mosaicism for der(21;21) and a ring chromosome 21. Three more patients had additional abnormalities, namely, t(10;12) (p11.1;q22), 15q microdeletion consistent with Prader-Willi syndrome and mosaic X/XXX.

CONCLUSIONS

All adults had balanced Rob-t. Unbalanced Rob-t were seen only in children. The unbalanced der(14;21) was our most common Rob-t followed by der(21;21) because the majority were ascertained in children with Down syndrome. The der(13;14) was the most common balanced Rob-t.