Deletions 6q26-q27 genotype phenotype correlations

Genotype phenotype correlations in deletions of chromosome 6q26-q27

The authors report on 8 patients with deletions of the distal segment of chromosome 6 (6q26-q27) and review 28 patients with deletions of this area from the literature. 29 patients (81%) had a terminal deletion 6q, 7 (19%) had interstitial deletions of this area. The whole group includes 9 prenatal cases, 4 patients diagnosed in infancy, 18 children and 5 adults. Among children and adults all (but one) were developmentally delayed. Structural brain anomalies were found in all prenatal cases and in 72% of infants, children and adults. These defects included microcephaly (7/32) and hydrocephalus (7/32). Facial dysmorphism was reported in 66% (21/32) but these features are not specific for diagnostic purposes. Seizures were noted in half of patients. Visceral defects were uncommon. Three patients had heart defects, two fetuses had kidney abnormalities. Out of 11 morbid genes located at the distal segment of 6q the authors selected two – DLL1 and TBP which may be responsible for most clinical manifestations. The TBP gene is considered to be responsible for cognitive and behavioral problems. The haploinsufficiency for the DLL1 gene may explain brain malformations, seizures, hypotonia and intellectual disability. The possible role of
other genes located in this area (ERMARD, PRKN, QKI) is also discussed.

Xie X. et al. “Genotype-phenotype correlations for putative haploinsufficient genes in deletions of 6q26-q27: report of eight patients and review of the literature”. “Global Med. Genetics” 2022, online.

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